The apartment turned out to be even better than in the pictures: it was cozy, comfortable, big and very stylish. Everything in the apartment is kept very tidy and clean, almost like a hotel room. There is everything one might need for a short (or longer stay): cooking equipment, towels, good wi-fi etc. There is an elevator to get to the third floor, which was very convenient too. I particularly liked the fact that there were aircons in every room - in winter you can keep warm, and in the summer it probably never gets too hot, which is important.
The location is great: the entrance of the building is to the main street that goes to Taksim, and it's 3-5 mins to the nearest metro station Osmanbey. There are small shops like Sok and bigger ones like Carrefour only 3-5 mins away from the flat.
With the windows facing the main street it may seem a bit noisy, but in the bedroom it's quiet and I could sleep well.
I'd like to thank Kerim again for making the stay easy: he was very approachable and responsive, helped us pick up the keys and answered all of the questions. I'd definitely recommend this flat.