Nice to hear from you again.
We received quite a lot of questions about "How to find a room inXYZ" in the past, but unfortunately there is little we can do except sharing links to useful websites and giving tips on what to write in your application mail. I saw that you already posted a similar question here on Wefugees a couple of months ago:
Did that help you?
Here are some other threads on Wefugees about flat-search in Hamburg: