Mark was a great host and communication was from the beginning to the end very easy and friendly as he replied to all my questions very fast. Moreover, Mark was very flexible concerning check-in and check-out times, which I really appreciated. I booked the apartment for my family, so myself was not staying there. Nevertheless I can confirm that the apartment was very tidy and clean and my parents felt very well there. The location is very well as it is easy reachable by S-Bahn, Metro and U-Bahn. The apartment itself is also located in a very quite place.
All in all, I can recommend Mark's apartment for everyone who wants to stay a few days in Berlin to do some sightseeing and get to know beautiful Prenzlauer Berg! :)