Igor has been an accurate host. The flat is nice, in a quiet area of the more chaotic Friedrichshain, quite close to everything you may need, maybe a bit cold/humid in this period but this is not Igor's fault considering that the heating is turned off in summer.
The flat was not 100% clean but we arrived as soon as another guest left, so I'm sure that was because Igor hasn't had time to properly arrange the place. Btw, suggested for your staying in Berlin.