Really nice appartement, very comfortable. The kitchen and living room are very spacious. I stayed in Christian's appartement for 4 days with friends and we had a very good time, I recommend! I haven't met Christian in person, but he was very nice, good communication.
The apartment is not that close from the center, so we took a U-Bahn ticket during our stay. Christian and his family live in the apartment, all their personal belongings were there. It didn't bother us since we stayed for a short amount of time.