diff --git a/_solutions/day-01/exercise1/level1.js b/_solutions/day-01/exercise1/level1.js
index f244852..825c89b 100644
--- a/_solutions/day-01/exercise1/level1.js
+++ b/_solutions/day-01/exercise1/level1.js
@@ -10,19 +10,62 @@ const webTechs = [
     'MongoDB',
   ]
 
+
+//   Declare an empty array;
+const newArr = Array()
+
+//   Declare an array with more than 5 number of elements
 const newArray = Array(6).fill('cats');
-newArray.push(7)
 
+//   Find the length of your array
+newArray.length
+
+//   Get the first item, the middle item and the last item of the array
+const firstItem = newArray[0]
+const lastItem = newArray[newArray.length-1]
+const middleItem = newArray[3]
+
+//   Declare an array called mixedDataTypes, put different data types in the array and find the length of the array. The array size should be greater than 5
+const mixedDataTypes = Array(6).fill('cats')
+mixedDataTypes.push(7)
+mixedDataTypes.length
+
+//   Declare an array variable name itCompanies and assign initial values Facebook, Google, Microsoft, Apple, IBM, Oracle and Amazon
 const itCompanies = Array('Facebook', 'Google', 'Microsoft', 'Apple', 'IBM', 'Oracle', 'Amazon')
 
+//   Print the array using console.log()
+console.log(itCompanies)
+
+//   Print the number of companies in the array
+itCompanies.length
+
+
+//   Print the first company, middle and last company
+const firstCompany = itCompanies[0]
+const lastCompany = itCompanies[itCompanies.length-1]
+const middleCompany = itCompanies[3]
+
+console.log(lastCompany)
+
+//   Print out each company
 for (let i = 0; i<itCompanies.length; i++) {
-    return (itCompanies[i].toLowerCase())
+    console.log(itCompanies[i])
 }
 
+//   Change each company name to uppercase one by one and print them out
+for (let i = 0; i<itCompanies.length; i++) {
+    itCompanies[i].toUpperCase()
+    console.log(itCompanies[i])
+}
+
+//   Print the array like as a sentence: Facebook, Google, Microsoft, Apple, IBM,Oracle and Amazon are big IT companies.
 const store = itCompanies.pop()
 const string = itCompanies.join(', ')
 const sentence = string + " and " + store + " are big IT Companies."
-// return sentence
+console.log(sentence)
+itCompanies.push(store)
+
+//   Check if a certain company exists in the itCompanies array. If it exist return the company else return a company is not found.
 
 for (let i = 0; i < itCompanies.length; i++) {
     let index = itCompanies.indexOf(itCompanies[i]) 
@@ -31,25 +74,49 @@ for (let i = 0; i < itCompanies.length; i++) {
     : console.log('This company does not exist in the array')
     }
 
+//   Filter out companies which have more than one 'o' without the filter method
 for (let i = 0; i < itCompanies.length; i++) {
         
     if (itCompanies[i].includes('o'))  {
         let matcher = itCompanies[i].match(/o/g).length
         if (matcher > 1) {
-            return itCompanies[i]
+            console.log(itCompanies[i])
         }
     } 
 }
 
-const sliced = itCompanies.slice(itCompanies.length-3, itCompanies.length)
+//   Sort the array using sort() method
+itCompanies.sort()
+
+//   Reverse the array using reverse() method
+itCompanies.reverse()
+
+//   Slice out the first 3 companies from the array
+
+const slicedFirstThree = itCompanies.slice(0, 3)
+
 
+//   Slice out the last 3 companies from the array
+const slicedLastThree = itCompanies.slice(itCompanies.length-3, itCompanies.length)
+
+
+//   Slice out the middle IT company or companies from the array
 const middle = itCompanies[Math.floor((itCompanies.length)/2)]
 
-const middleIndex = Math.floor((itCompanies.length)/2)
 
-itCompanies.splice(middleIndex,1)
+//   Remove the first IT company from the array
+const removedFirst = itCompanies.shift()
 
-itCompanies.length = 0
+itCompanies.unshift('Oracle')
+
+//   Remove the middle IT company or companies from the array
+const middleIndex = Math.floor((itCompanies.length)/2)
+const removedMiddle = itCompanies.splice(middleIndex,1)
 
+itCompanies.splice(middleIndex, 0, ...removedMiddle);
 
+//   Remove the last IT company from the array
+const removedLast = itCompanies.pop()
 
+//   Remove all IT companies
+itCompanies.length = 0
\ No newline at end of file
diff --git a/_solutions/day-01/exercise1/level2.js b/_solutions/day-01/exercise1/level2.js
index 5a43c2b..ba76f03 100644
--- a/_solutions/day-01/exercise1/level2.js
+++ b/_solutions/day-01/exercise1/level2.js
@@ -1,8 +1,13 @@
 // Exercise 1 - Level 2
 
+// 1. Create a separate countries.js file and store the countries array into this file, create a separate file web_techs.js and store the webTechs array into this file. Access both file in main.js file.
+
 const countries = require('./countries.js');
 const webTechs = require('./ web_techs.js');
 
+
+// 2. First remove all the punctuations and change the string to array and count the number of words in the array
+
 const str = countries.toString()
 
 const modifiedStr = str.replace(/[^\w]/g, ' ')
@@ -12,6 +17,12 @@ const newArray = modifiedStr.split(' ')
 const numOfWords = newArray.length
 
 
+// 3. In the following shopping cart add, remove, edit items:
+    // add 'Meat' in the beginning of your shopping cart if it has not been already added
+    // add Sugar at the end of you shopping cart if it has not been already added
+    // remove 'Honey' if you are allergic to honey
+    // modify Tea to 'Green Tea'
+
 const shoppingCart = ['Milk', 'Coffee', 'Tea', 'Honey']
 
 if (!shoppingCart.includes('Meat')) {
@@ -25,6 +36,7 @@ if (!shoppingCart.includes('Sugar')) {
 shoppingCart[3] = 'Green Tea'
 
 
+// 4. In countries array check if 'Ethiopia' exists in the array if it exists print 'ETHIOPIA'. If it does not exist add to the countries list.
 
 if (!countries.includes('Ethiopia')) {
     countries.push('Ethiopia')
@@ -33,6 +45,7 @@ if (!countries.includes('Ethiopia')) {
 }
 
 
+// 5. In the webTechs array check if Sass exists in the array and if it exists print 'Sass is a CSS preprocess'. If it does not exist add Sass to the array and print the array.
 
 if (!webTechs.includes('Sass')) {
     webTechs.push('Sass')
@@ -41,6 +54,9 @@ if (!webTechs.includes('Sass')) {
     console.log('Sass is a CSS preprocess')
 }
 
+
+// 6. Concatenate the following two variables and store it in a fullStack variable.
+
 const frontEnd = ['HTML', 'CSS', 'JS', 'React', 'Redux']
 const backEnd = ['Node', 'Express', 'MongoDB']
 
diff --git a/_solutions/day-01/exercise1/level3.js b/_solutions/day-01/exercise1/level3.js
index b34942a..cae1c25 100644
--- a/_solutions/day-01/exercise1/level3.js
+++ b/_solutions/day-01/exercise1/level3.js
@@ -1,29 +1,37 @@
 // Exercise 1 - Level 3
 
-const countries = require('./countries.js');
+// 1. The following is an array of 10 students ages: 
 const ages = [19, 22, 19, 24, 20, 25, 26, 24, 25, 24]
 
+// - Sort the array and find the min and max age
 const sortedArray = ages.sort()
-
 const minAge = sortedArray[0]
 const maxAge = sortedArray[sortedArray.length-1]
 
+// - Find the median age(one middle item or two middle items divided by two) 
 const medianAge = (sortedArray[4] + sortedArray[5])/2
 
+// - Find the average age(all items divided by number of items)
 const averageAge = (sortedArray.reduce((number, a) => number + a, 0))/sortedArray.length
 
+// - Find the range of the ages(max minus min) 
 const rangeAge = maxAge - minAge
 
+// - Compare the value of (min - average) and (max - average)
 const compareAge = (maxAge - averageAge)-(minAge - averageAge)
 
 
+// 2. The following is a countries array:
+const countries = require('./countries.js');
 
-
+// Slice the first ten countries from the countries array
 const slicedCountries = countries.slice(0,10)
 
+// Find the middle country(ies) in the countries array
 const middleCountry = countries[5]
 
-const firstHalf = countries.slice(0,6)
+// Divide the countries array into two equal arrays if it is even. If countries array is not even , one more country for the first half.
 
+const firstHalf = countries.slice(0,6)
 const secondHalf = countries.slice(6,11)
 
diff --git a/_solutions/day-01/exercise2/level1.js b/_solutions/day-01/exercise2/level1.js
index 367d071..9519554 100644
--- a/_solutions/day-01/exercise2/level1.js
+++ b/_solutions/day-01/exercise2/level1.js
@@ -1,5 +1,7 @@
 // Exercise 2 - Level 1
 
+// 1. If user is 18 or older , give feedback:'You are old enough to drive' but if not 18 give another feedback stating to wait for the number of years he needs to turn 18.
+
 let age = 34
 
 if (age <18) {
@@ -10,6 +12,8 @@ if (age <18) {
 }
 
 
+// 2. Compare the values of myAge and yourAge using if … else. Based on the comparison and log the result to console stating who is older (me or you).
+
 if (age > 29) {
     let years = age - 29
     console.log(`You are ${years} years older than me.`)
@@ -21,6 +25,8 @@ if (age > 29) {
 }
 
 
+// 3. If a is greater than b return 'a is greater than b' else 'a is less than b'. 
+
 let a = 2
 let b = 2
 
@@ -33,6 +39,8 @@ if (a > b) {
 }
 
 
+//4. Even numbers are divisible by 2 and the remainder is zero. How do you check, if a number is even or not using JavaScript?
+
 let number = 10
 
 if (number%2 === 0) {
diff --git a/_solutions/day-01/exercise2/level2.js b/_solutions/day-01/exercise2/level2.js
index 02ee6dd..6381d95 100644
--- a/_solutions/day-01/exercise2/level2.js
+++ b/_solutions/day-01/exercise2/level2.js
@@ -1,6 +1,12 @@
 // Exercise 2 - Level 2
 
-let score = 75;
+// 1. Write a code which can give grades to students according to theirs scores:
+// 80-100, A
+// 70-89, B
+// 60-69, C
+// 50-59, D
+// 0-49, F
+// let score = 75;
 
 if (score >= 90 && score <= 100) {
     console.log('A');
@@ -17,6 +23,12 @@ if (score >= 90 && score <= 100) {
 }
 
 
+// 2. Check if the season is Autumn, Winter, Spring or Summer. If the user input is :
+// September, October or November, the season is Autumn.
+// December, January or February, the season is Winter.
+// March, April or May, the season is Spring
+// June, July or August, the season is Summer
+
 let month = 'September'
 
 if (month === 'September' || month === 'October' || month === 'November') {
@@ -26,11 +38,13 @@ if (month === 'September' || month === 'October' || month === 'November') {
 } else if (month === 'March' || month === 'April' || month === 'May') {
     console.log('The season is Spring')
 } else if (month === 'June' || month === 'July' || month === 'August') {
-    console.log('The season is Summer') }
+    console.log('The season is Summer') 
+}
 
 
-let day = 'FriDAY'
+// 3. Check if a day is weekend day or a working day. Your script will take day as an input.
 
+let day = 'FriDAY'
 let lowered = day.toLowerCase()
 
 switch(lowered){
diff --git a/_solutions/day-01/exercise2/level3.js b/_solutions/day-01/exercise2/level3.js
index a237bfa..b8d434f 100644
--- a/_solutions/day-01/exercise2/level3.js
+++ b/_solutions/day-01/exercise2/level3.js
@@ -1,5 +1,7 @@
 // Exercise 2 - Level 3
 
+// 1. Write a program which tells the number of days in a month. Then, consider leap year.
+
 const currentDate = new Date();
 const currentYear = currentDate.getFullYear();
 
diff --git a/_solutions/day-01/exercise4/level1.js b/_solutions/day-01/exercise4/level1.js
new file mode 100644
index 0000000..881eb66
--- /dev/null
+++ b/_solutions/day-01/exercise4/level1.js
@@ -0,0 +1,63 @@
+// Exercise 4 - Level 1
+
+// 1. Declare a function fullName and it takes firstName, lastName as a parameter and it returns your full - name.
+
+const fullName = function (firstName, lastName) {
+    console.log(firstName + " " + lastName) 
+}
+
+// 2. Declare a function addNumbers and it takes two two parameters and it returns sum.
+
+const addNumbers = function (a, b) {
+    console.log(a + b)
+}
+
+// 3. Area of a circle is calculated as follows: area = π x r x r. Write a function which calculates _areaOfCircle
+
+const areaOfCircle = function (radius) {
+    const circleArea = Math.PI * radius * radius 
+    console.log(`The area of the circle is ${circleArea}`)
+}
+
+// 4. Temperature in oC can be converted to oF using this formula: oF = (oC x 9/5) + 32. Write a function which convert oC to oF convertCelciusToFahrenheit.
+
+const convertCelciusToFahrenheit = function (celsius) {
+    const fahrenheit = (celsius * 9/5) + 32
+    console.log(`${celsius} degrees Celsius is the same as ${fahrenheit} degrees Fahrenheit`)
+}
+
+// 5. Body mass index(BMI) is calculated as follows: bmi = weight in Kg / (height x height) in m2. Write a function which calculates bmi. BMI is used to broadly define different weight groups in adults 20 years old or older.Check if a person is underweight, normal, overweight or obese based the information given below.
+
+// The same groups apply to both men and women.
+// Underweight: BMI is less than 18.5
+// Normal weight: BMI is 18.5 to 24.9
+// Overweight: BMI is 25 to 29.9
+// Obese: BMI is 30 or more
+
+
+const checkBMI = function (weight, height) {
+    const bmi = weight / (height * height)
+    if (bmi >= 30) {
+        console.log(`Your BMI is ${bmi} which is 'obese'.`);
+    } else if (bmi >= 25 && bmi <= 29.9) {
+        console.log(`Your BMI is ${bmi} which is 'overweight'.`);
+    } else if (bmi >= 18.5 && bmi <= 24.9) {
+        console.log(`Your BMI is ${bmi} which is 'normal weight'.`);
+    } else if (bmi < 18.5) {
+        console.log(`Your BMI is ${bmi} which is 'underweight'.`);
+    }
+}
+
+
+// 6. Write a function called checkSeason, it takes a month parameter and returns the season:Autumn, Winter, Spring or Summer.
+
+const checkSeason = function (month) {
+    if (month === 'September' || month === 'October' || month === 'November') {
+        console.log('The season is Autumn')
+    } else if (month === 'December' || month === 'January' || month === 'February') {
+        console.log('The season is Winter')
+    } else if (month === 'March' || month === 'April' || month === 'May') {
+        console.log('The season is Spring')
+    } else if (month === 'June' || month === 'July' || month === 'August') {
+        console.log('The season is Summer') }
+}
diff --git a/_solutions/day-01/exercise4/level2.js b/_solutions/day-01/exercise4/level2.js
new file mode 100644
index 0000000..94105b1
--- /dev/null
+++ b/_solutions/day-01/exercise4/level2.js
@@ -0,0 +1 @@
+// Exercise 4 - Level 2
\ No newline at end of file
diff --git a/_solutions/exercise4/level1.js b/_solutions/exercise4/level1.js
deleted file mode 100644
index daa5ad2..0000000
--- a/_solutions/exercise4/level1.js
+++ /dev/null
@@ -1,22 +0,0 @@
-// Exercise 4 - Level 1
-
-// 1. Declare a function fullName and it takes firstName, lastName as a parameter and it returns your full - name.
-
-
-
-
-// 2. Declare a function addNumbers and it takes two two parameters and it returns sum.
-
-// 3. Area of a circle is calculated as follows: area = π x r x r. Write a function which calculates _areaOfCircle
-
-// 4. Temperature in oC can be converted to oF using this formula: oF = (oC x 9/5) + 32. Write a function which convert oC to oF convertCelciusToFahrenheit.
-
-// 5. Body mass index(BMI) is calculated as follows: bmi = weight in Kg / (height x height) in m2. Write a function which calculates bmi. BMI is used to broadly define different weight groups in adults 20 years old or older.Check if a person is underweight, normal, overweight or obese based the information given below.
-
-// The same groups apply to both men and women.
-// Underweight: BMI is less than 18.5
-// Normal weight: BMI is 18.5 to 24.9
-// Overweight: BMI is 25 to 29.9
-// Obese: BMI is 30 or more
-
-// 6. Write a function called checkSeason, it takes a month parameter and returns the season:Autumn, Winter, Spring or Summer.
\ No newline at end of file