I was in negotiations with HVB and Commerzbank. I choose Commerzbank, which had a slightly higher interest rate but way much better communication with me. I was communicating with the guy in charge of the wealth management, this may also helped a lot. ;)

Loans lower 400k are easier to issue, I learned in the process. Because >400k has much more requirements for the bank on collateral required by the regulation authorities.

I'm not in Germany but an acquaintance has a 20 year fixed rate mortgage in Germany from one of the Sparkassen (Flat in Berlin).