We booked 3 nights for a family stay in Berlin but left after one. Hardly any of us could sleep because of the neighbours partying all night. Someone was standing in the stairway screaming at the top of their lungs at 2 am.
I understand that this is not something that happens here all the time, and that we were unlucky. The apartment in itself is nice and the communication & check in worked well. We got 100€ refund for the noise.