Karsten place is great. We stayed 3 nights in Karsten airbnb. Karsten was very responsive on emails prior to our venue. He was in the flat to welcome us in, he showed us around in the flat. The decoration is very good. very atypical and that's what we were looking for. Something not ordinary. Karsten is a very honest person.
The flat is very well located. We had diner in the second best rated German restaurant on Timeout, which was literally 2 minutes walk from the flat. There are plenty of places to eat on the street (some places close at 5pm), but you can find diner. There is a supermarket as well a few minutes walk.
On our first day we walked from the flat to checkpoint charlie, which is a straight line. it took us about 1 hour 30, but it is a nice walk.
Plenty of things to do around the flat.
The flat is big and comfortable, you will find all the amenities you need. You can make yourself a tea or coffee, buy some food and put it in the fridge. The internet wasn't great. We wanted to watch Netflix to relax on the evening but the connection wasn't powerful.
I will recommend the flat 100%!