The place is clean and looks as advertised. Good wifi (>70Mbps download and upload most of the time). It's near the ferries, subway, there are a lot of shops nearby. My only issues were:
1) English communication (Beyazıt was very helpful, it just takes a little bit of effort to understand each other)
2) The room is a little bit cold in the winter but it was -2C° when I arrived which is uncommon for Istanbul. I did not ask Beyazıt whether he has an electric heater.
I recommend this place.
Thank you for hosting me!