What a nice apartment in a superb, though quiet, central Kreuzberg location. We stayed for three nights, two adults and two 15yr olds.
Arnd's is a comfortable, light apartment, with ample living space and plenty of closets to keep luggage out of side. Clean and complete kitchen. Efficient bathroom (toilet/shower/basin plus washing machine). Good WiFi.
The 160cm wide sofabed in the sitting room was comfortable for two; there were good, large separate beds in the spacious bedroom. Quality bedding, towels etc.
Arnd was very friendly and flexible: we arrived two hours late on short notice, we left late in the afternoon.
When arriving by train, get off at Ostbahnhof and take a 4 minute EUR 6 taxi, or walk for 10 minutes.
For rental bikes, Arnd pointed us to yaambike, a ten minute walk to the start of the East Side Gallery on the other side of the river, across the road from Ostbahnhof.
The groundfloor flat is on a wide, quiet street just off Mariannenplatz. Tens (hundreds?) of Kreuzberg cafes and restaurants are within a five minute walk's reach. Cycling to the Brandenburger Gate or Museum Island takes 20 minutes.
We had a great stay. We'll be back!