Me and my girlfriend stayed at Serda's apartment for a couple of days, and we really enjoyed it! The house is super-well located, right in the middle of Friedrichshain. You have bars, cafeterias, places to eat and hip shops just a few steps away; S-Bahn and U-Bahn are five minutes walk. The room is huge and perfectly cleaned. Serda is the perfect host: he is very kind and replies quickly to every message, but he is also discreet and let you live the house as you please.