A fine and bright room in a well-equipped apartment situated in a courtyard, which is pretty quiet overall, though there can be some noise, also during the night/early in the morning.
It's not really close to the city centre, but the subway is very conveniently situated 50 metres down the road and Neukölln is a lively enough neighborhood anyway with everything you need just around the corner.
I only saw Osam when I arrived and left. He's a very respectful host and communication with him goes smoothly. Definately recommended!