My only complaint is that the place is listed as an apartment whereas it is (as it is indeed named) a room in an apartment.
Having said that, our stay was very enjoyable: the location is invaluable, the room was quiet and comfortable, our needs were fully met (including flexibility regarding check out time) and the host - Victor, Diana's brother - was kind and helping. Therefore, if one seeks a room near Alexanderplatz, I would definitely recommend this place.