I have to give Deniz and Dündar all the five stars for the apartment! We stayed with a group of people in the apartment and all went very well!
The best part was Deniz! She is super friendly and helpful! She made reservations, gave us information when needed and was just overall a very nice and cool person. If I could I would give her more than five stars!
The apartment is quiet central, although you really have to keep in mind that it is on a steep hill. But you can always take a taxi (from the Taksim it costs you around 5-10 lira).
The rooms in the apartment look exactly like in the pictures on airbnb. The livingroom and one bedroom face the main street, so if you sleep there, it could be a little bit loud. But Deniz and Dündar have plenty of earplugs (my friends sleped very well in that room).
The apartment was very clean!
I would definitely recommend that place! If I ever come back I would want to stay in a place that belongs to Deniz and Dündar. The apartment made the stay for us a a group perfect!