Marie's place is a very good place to stay in Berlin. It's very clean, as a guess you have to much privacy because the spaces are separated by doors closed almost all the time, it's very quiet so you can have a good sleep after a long day walking, there is a lift in the building so you don't have to carry your luggage. Marie is so nice and kind, her husband is too. She speaks english very well so you don't have any trouble with the language if you don't speak german. The bed is very comfortable and the view through the windows is pretty nice.
The neighborhood is safe, quiet and pretty. You have the metro station very close to the apartment (around 4 blocks), tram and buses, so you will not have any issue with transportation, despite the place is not so close to the touristic places, you will be there in around 15-20 minutes. I highly recommend Marie's place.