Christian was a great host: friendly and always ready to help us. His home is located on a peaceful street, in a lovely old building, just 5 minutes away from Schonhauser Allee U-Bahn and S-Bahn station. From there you can very easily reach both Tegel airport and the city center. The room is clean, organized, big enough for 2 persons. Everything is modern in Christian's home so there won't be any shortages.
I would definitely recommend this place to anyone who's looking for a cool place to stay in Berlin.