I didn't get a chance to talk with Rene and Marysia in person since they were on vacation, but they kindly arranged for a friend to meet me in their flat at night to hand me the keys. They were also quick to respond to questions I emailed them. The flat itself is nice. Everything functions well, and the bedroom is spacious. The location was convenient too: it was a block away from a grocery store, a block away from an U-bahn stop, and a few blocks away from the 142 bus which I took from Berlin Hbf.