Axel's place is the best. Located just a block from a U Bahn station, where you can go anywhere in the city. Also less than a block from a mini market and a pharmacy. Lots of nice eating places nearby. It was perfectly clean, everything worked as it should, plenty of toilet paper and all the kitchenware you might need to prepare a hot breakfast or simple dinner.
We were met by Axel himself, and he is an excellent host. He gave us lots of tips about restaurants and moving around using the subway.
All in all, this is by far, one of the best AirBnBs I've ever stayed in and would definitely return the next time we are in Berlin.