Our experience of staying in Katia's apartment was all in all very nice. We really liked the furnishing, and her roommate was really nice and helpful.
However, the apartment was pretty dusty and cold. Additionally, the kitchen was not very inviting because of the poor standards of hygiene and missing service. In spite of that, we got a very authentic experience of Berlin because of the location of the apartment, which was in an area where we did not experience as many tourists as we did in other parts of Berlin. Lastly, we would consider staying in this apartment again during the summer, all though we were disappointed by the absence of the cat mentioned in other reviews.