If I ever return to Berlin, I am definitely booking another stay at Steffen's place. It is quiet, clean, and in a good location. Plus, having access to a washer/dryer is awesome. One thing I will recommend, especially for those coming from out of the country is to make sure you have cash to cover the tax that city of Berlin requires.
Steffen is a great host and responded to my messages instantly, despite traffic causing me to check in about an hour after I originally planned. I am very happy with my experience and appreciate Steffen for allowing me to stay in this lovely little apartment!