Hermann is a really helpful host: gives you a lot of information about the city, the neighborhood and the public transport. When you had a problem, he came immediately. And he also gave us a free ride to the bus station! :)
The house is not central, although you can reach the closest station in about 15 minutes and more 10 minutes to go to the center.
The house is really good. Simple, but really functional. There are no room, but the four of us were comfortable in the two double beds. The kitchen is good, but there is no oven.
The only problem was the bathroom, because we were in four guests and, as mentioned in former comments, there is only a hot water reservoir for the bathroom. Therefore, sometimes, in the middle of the shower the water got cold. If you are in more than two person, you would probably have to wait around 30 minutes to take a shower. That's a little bit annoying.

Overall, it was a good stay and really value for money!