I have spend a full week at Chris' apartment in July while taking a German course.
Both Chris and his mate welcomed me warmly. The apartment was located in a quiet street of the central district of Kreuzberg, that is only 5 minutes away by foot from metro and a large bar/restaurant area. The flat was large, cosy and sunny. I have enjoyed the large room (over 20 m2) I have rented. The bed was large and comfortable. In addition, the bathroom was spacious, comfortable and very clean. I can only recommend Chris apartment to Berlin visitors.