Lovely apartment in a well connected area. Very easy to get to Alexanderplatz station though there's plenty of cafes/restaurants to visit nearby.
The apartment is nicely decorated and everything is very functional - similar (if not better) than the pictures presented. Only thing is the apartment is up a few flights of stairs but nothing too major.
Overall, had a lovely stay in Kerstin's apartment. We'd recommend it to anyone wanting to stay in Berlin.