My boyfriend and I stayed with Sophia for a few days during our visit to Berlin.
First, the apartment is in a great location. You are able to walk to several public transportation options, and there are tons of restaurants, bars, and shops in the area. I've stayed in Kreuzberg twice now and really love it. The room is perfectly comfy, quiet, and has a ton of natural light.
Sophia is very kind and happy to answer any questions you may have. She was very flexible with our check-in, even when our flight was later than expected. She is a great host, and I would recommend her and her place to anyone looking for a great spot in Berlin.