Kristina’s place is nice, a little further out of Berlin than expected but not difficult if you don’t mind walking a bit (5-10 mins from nearest U-Bahn, which we found to be Richard-Wagner-Straße rather than Charlottenburg U). Kristina herself was very thoughtful and helpful, the snacks left for us in the apartment were much appreciated! One slight issue was that the walls are quite thin so it’s very easy to hear neighbours talking etc but this didn’t really bother us. Would recommend Kristina’s flat as a good, inexpensive but nice place to stay in Berlin, and Kristina herself as an excellent host.