[contents] fix typo in self intro (#158)

contents/self-introduction.md

@@ -52,7 +52,7 @@ Prepare a self introduction that follows the following outline (inspired by "Cra
 
 1. A sentence about your current or most recent role.
 1. A few sentences about your (academic) background. What did you focus on?
-1. Some sentences about your professional experience after school/university. Where did you work? What projects did you deal with? What where typical challenges and tasks? Which technologies did you use?
+1. Some sentences about your professional experience after school/university. Where did you work? What projects did you deal with? What were the typical challenges and tasks? Which technologies did you use?
 1. Finish with a statement saying why you are seeking a new job opportunity and why you are interested in the role you applied for.
 
 ## Examples