Sebastian was really convenient and made sure to be there when I arrived. On top of that he gave some advice on the clubs and bars to visit in Berlin.
The appartment was really huge and at a top place, the S-Bahn station Ostkreuz is really close and there are many restaurants and bar in the quarter. The room was indeed big and the couch as well, so even my taller friend fitted in! Even if it's at a top place, the appartment is well isolated for the noise coming from the street.
We really had a nice stay.