The flat itself is really nice and definitely suitable for a longer stay. Martin is also very responsive and kind - whenever I had a question he instantly got back to me and helped me with whatever I needed (thanks for that)!
The location itself is also extremely good as it is central (close to Potsdamer Platz). However, I must admit that I was a little bit surprised by the building and the street (was pretty dirty) when I arrived.
All in all: Good place and I’d come back!