I was recently interviewed with amazon for SDE at Berlin.
The interviewer was friendly and I received question related to dynamic programming.
We had little over 60 mins call over all.

1. First 30 minutes I had a behavioral round where the interviewer gave their introduction and asked me "Tell me about a time when you had to work on a project in which you had no idea where to start? How did you proceed in the situation? How did you finish the task? What was the result?" The interviewer told "very impressive"
2. Next 30 minutes I had a question on dynamic programming which I was able to solve
3. Another 5 minutes where we discussed on questions I had.

The interviewer seemed to have given very positive response that "Hope to see you soon. As far as next round is concerned you will have interview with 4 other people and will see what the recruiting team decides. I am very impressed with your skills!!"

I don't get it why I was rejected?

After careful consideration and review of your application, we have decided to progress with other candidates for this role, and are not able to provide additional feedback or information about this decision.