Mehmet was a great host, he didn't mind our late check in (about midnight) and when we got to his place, he fixed us some food, so we were not searching for it at night. Also he speaks quite good English, which is not very common in Istanbul. Thank you Mehmet!
About the place: the best part of it is location, it is a very nice historical neighborhood called Balat, where lots of gastro hipster places are located. The appartment itself is on the roof, if you have troubles sleeping, be careful as it is located right next to the mosque and every morning at 5.45 you'll be awaken by a morning call for prayer. Also it faces the road, where the traffic is quite busy (like everywhere in Istanbul).
One last thing: if you have an allergy to dust, tobacco smoke or suffer from asthma, it would be quite challenging for you stay here. Parents should mind the stairs (as I mentioned it is on the roof).
All in all we enjoyed our stay.