Stella was and reactive when we contacted her. The flat and the room is very nice and clean and with all the equipment necessary.
The area is convenient to reach central Berlin and has lots of nice/trendy bars, restaurants, parks, historical sites.
Stella is a really accommodating host and if you arrive before check-in time, there are lockers just downstairs the flat to leave your suitcases and go visit Berlin without hassle. I would recommend 100%!