We stayed at Su's place for two weeks.
The apartment has 3 seperate bedrooms, 1 living room, kitchen, bath with toilet and a 2nd separate toilet
There is also a terrace one floor above the apartment from where you can see the Galata Tower and even the Hagia Sophia from one of the corners.
The apartment was clean and tidy with fast Internet. Kitchen is equipped with anything you might need (but I suggest eating outside since the food outside is cheap and great).
Unfortunately we had a plumbing issue the first day but it was fixed within the hour. So no biggy. Communication with Su was great.
Locationwise the apartment is located in Beyoglu with a lot of shops, restaurants and bars all around the place.
The Grand Bazaar is around 20-30 mins away by foot. Taksim square about 5 minutes and the Istiklal Street around 2-3mins by foot. The relatively new Galata Port which has a lot of "more Western" restaurants and shops is also just a couple minutes away. The ferry pier to reach other parts of Istanbul aswell as other means of public transport are nearby.
If you want to explore Istanbul this is a very good area.
Overall it as well located, clean and super functional apartment. I can definitely recommend staying there for your visit.
Su and Enis were good hosts with very good communication before aswell as well as during our stay.