I stayed in Sören's apartment for 4.5 months and would highly recommend it as a base for both short and longer term stays in Berlin. The apartment is bright, really well laid out, beautifully restored, fully equipped and is located in a beautiful and historic part of the city with a village feel. There's lots of really cool bars and restaurants nearby, as well as great transport links to the rest of the city.
Sören was a fantastic host, going above and beyond - he was very flexible with both check in and check out times..... meeting me on arrival to help me settle in, giving me lots of great recommendations for the area and even gave me his bike for my stay! I very rarely needed to contact Sören, but any time I did he responded straight away!