If I could give 6 stars to Ali, I would!
He was incredibly helpful during our stay -- I could not sleep on the first night because of the street noise, and he fixed the problem the best he could, my parents needed a ride to the airport, and he offered airport service as well, he left us water in the flat and gave us a map with recommendations around Istanbul.
The place itself is VERY central in the Sultanahmet area, it was clean, and nice to live for a few days.
Warmly recommend Ali and his apartment!