The apartment was sparkling clean, very comfortable, had all appliances you would require and was perfectly located. Very close from one of the main subway lines, so is easy to reach the city center and the airport. It's also just near the bus line for the stadium (if you want to go to some concerts) or for Donauinsel, which was a nice discovery for us ( a must see location, especially in the summer)
We didn't meet Christian in person, but the communication between us was always quick and great overall. He permitted us to check-in earlier.
Thanks for all, Christian!