The whole interview process took me 1 hour.
Everybody was very friendly and talking to me in German (besides security).
The interview took like 15 minutes and he just asked:
-how and when did you meet
-what does he do for a living
-what degree do you have/what are you planning to do for a living in the u.s.
-when do you enter the united states
Then he told me that my visa is approved and that I'll receive it in about a week.