Marc's apartment is great for a stay in Berlin. The location is great. There is a metro station nearby and most of the city centre is within walking distance anyway. The neighborhood is very quiet and calm, so it's a nice place to return to after a busy day in the city.
The apartment itself is also great. It has nice, large windows to let in light and fresh air. It is stylish, clean and comfortable. As mentioned, a nice place to rest after exhausting yourself in Berlin.
Marc is also a great host. He has clear instructions for everything and responds very quickly to messages.