Perfect place!!! The room is spacious and super clean and the bed big and comfortable. Not having access to the kitchen was no problem at all since there are plenty of good and cheap cafes and restaurants around the corner. The location overall is as convenient as it gets. Great and lively neighborhood (the room was very quiet at night though). Lots of sights in walking distance and everything further away you can easily reach by public transport.
Johannes (who is living in the Appartment as well but was out most of the time) was very nice and extremely helpful with all my questions. I highly recommend the place and will definitely be back on my next trip to Berlin!