Hosts were super friendly. The place is located at a great location. There are some things we wanted to note for other future guests:
1. The windows cannot be partially open. So it's either cold or stuffy in the flat. Probably not a huge problem in summer. We didn't use A/C.
2. Ceilings are low, which might feel uncomfortable if you are tall
3. The water is not potable and shampoo at the flat is quite generic. So if it's important for your hair, worth bringing your own shampoo. Make sure to bring some drinkable water too.
4. There is not much space in rooms, the flat itself is quite small.
Overall we enjoyed the stay, but we probably won't stay there again in Istanbul.