diff --git a/01_Day_Introduction/01_day_starter/helloworld.js b/01_Day_Introduction/01_day_starter/helloworld.js
index 8c9e2c0..b3721cf 100644
--- a/01_Day_Introduction/01_day_starter/helloworld.js
+++ b/01_Day_Introduction/01_day_starter/helloworld.js
@@ -1 +1,2 @@
-console.log('Hello, World!')
\ No newline at end of file
+console.log('Hello, World!')
+//Print something with JS code.
diff --git a/02_Day_Data_types/02_day_starter/main.js b/02_Day_Data_types/02_day_starter/main.js
index 7762908..3572615 100644
--- a/02_Day_Data_types/02_day_starter/main.js
+++ b/02_Day_Data_types/02_day_starter/main.js
@@ -1 +1,12 @@
-// this is your main.js script
\ No newline at end of file
+// this is your main.js script
+
+let string = 'JavaScript'
+let firstLetter = string[0]
+console.log(firstLetter) // J
+let secondLetter = string[1] // a
+let thirdLetter = string[2]
+let lastLetter = string[9]
+console.log(lastLetter) // t
+let lastIndex = string.length - 1
+console.log(lastIndex) // 9
+console.log(string[lastIndex]) // t
diff --git a/05_Day_Arrays/05_day_starter/scripts/main.js b/05_Day_Arrays/05_day_starter/scripts/main.js
index 50cc07e..ee14bd8 100644
--- a/05_Day_Arrays/05_day_starter/scripts/main.js
+++ b/05_Day_Arrays/05_day_starter/scripts/main.js
@@ -1,3 +1,63 @@
-console.log(countries)
-alert('Open the browser console whenever you work on JavaScript')
-alert('Open the console and check if the countries has been loaded')
\ No newline at end of file
+// //Exercise in Array
+// Exercise Level 1
+/**
+ * 
+ * ## 💻 Exercise
+
+### Exercise: Level 1
+
+```js
+const countries = [
+  'Albania',
+  'Bolivia',
+  'Canada',
+  'Denmark',
+  'Ethiopia',
+  'Finland',
+  'Germany',
+  'Hungary',
+  'Ireland',
+  'Japan',
+  'Kenya'
+]
+
+const webTechs = [
+  'HTML',
+  'CSS',
+  'JavaScript',
+  'React',
+  'Redux',
+  'Node',
+  'MongoDB'
+]
+```
+
+1. Declare an _empty_ array;
+2. Declare an array with more than 5 number of elements
+3. Find the length of your array
+4. Get the first item, the middle item and the last item of the array
+5. 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
+6. Declare an array variable name itCompanies and assign initial values Facebook, Google, Microsoft, Apple, IBM, Oracle and Amazon
+7. Print the array using _console.log()_
+8. Print the number of companies in the array
+9. Print the first company, middle and last company
+10. Print out each company
+11. Change each company name  to uppercase one by one and print them out
+12. Print the array like as a sentence: Facebook, Google, Microsoft, Apple, IBM,Oracle and Amazon are big IT companies.
+13. Check if a certain company exists in the itCompanies array. If it exist return the company else return a company is _not found_
+14. Filter out companies which have more than one 'o' without the filter method
+15. Sort the array using _sort()_ method
+16. Reverse the array using _reverse()_ method
+17. Slice out the first 3 companies from the array
+18. Slice out the last 3 companies from the array
+19. Slice out the middle IT company or companies from the array
+20. Remove the first IT company from the array
+21. Remove the middle IT company or companies from the array
+22. Remove the last IT company from the array
+23. Remove all IT companies
+ */
+ //Empty array
+const animals = ['lion','dog','cat','pig','monkey'];
+console.log(`This is my array:  ${animals}`)
+const myArrayLength = animals.length;
+console.log(`This array length is: ${myArrayLength}`);