Oleg's place is nice and clean and very spacious. It's conveniently located near a metro station so every thing is easily accessible.
We didn't get to meet Oleg but his flatmate Simo is quite friendly and he explained everything to us really well. He is full of joy and fun to be around. Communication with Oleg, however, was fast and he gave us all the information we needed beforehand for the check-in.
Oleg, in addition to the essentials, had left us some food, snacks, tea and milk which says something. We were also allowed to use anything we needed.
We enjoyed our stay a lot and will love to come back when in Berlin.