We arrived much earlier in the morning at the apartment than discussed with Mustafa, but luckily his colleague Yeliz was already in the house and welcomed us. Although the room wasn't cleaned yet, we could leave our luggage in the room and already explore the city. Yeliz gave us a map and explained us everything with very good tips where to go when you only have one or two days in Istanbul.
The apartments are managed in a professional way, there is a reception which seemed permanently occupied.

The room was completely sufficient - big enough for 2 people. There is a fridge in the room and the bathroom was completely new.

The room was very clean and I it's perfect for one weekend in Istanbul! (Shuttle bus station to both airports is also quite near)