The apartment is great and matches the pictures, we appreciated that there were 4 rooms which gives more privacy. The apartment is within a walking distance to the Havaist station, ferries, and all public transportation, and is in a quite area but very close to the center of kadikoy (also within walking distance).
Demir was helpful and supportive when we had some issues with heating and fixed them asap.
The only inconvenience was that the house is on the 3rd floor, which was a bit tough in carrying luggage up and down. But the apartment is also situated in a flat area, so you get to avoid carrying your luggage across any hills.
Overall the stay was great and would recommend it to anyone considering to stay in Kadikoy.