I had a lovely time at Katja's place! Despite not meeting her in person because she went on a trip, we managed to communicate and to organize my check-in without any problems. Katja was very accommodating, understanding and answered any questions I had. The room is as described with lots of light, comfortable bed and a nice balcony. The location is great if you're looking to do relaxing East Berlin things. Rent a bike when you're there! I'd stay there again.