Reserving the apartment went smoothly and Wolf answered every inquiry patiently and very promptly! He sent us options and detailed information about getting to the apartment, with prices and travel times. When we checked in, he and his wife explained all the details about the apartment and gadgets.
Apartment is as described and even looks better than in the pictures. Very clean, modern, in an excellent neighborhood, quite close to the sights on foot (but U-Bahn and tram stops are quite close too), really comfortable (you won't find bigger or more comfortable sofa anywhere!), with all the amenities you might need. As a bonus, some basic items were left in the pantry we could use. WiFi worked perfectly. Additionally, Wolf went out of his way to inquire through email during our stay if we needed anything.
I would recommend it to friends wholeheartedly or stay in it again. Vielen Dank, Wolf :)