Probably it was one of the best stays ever! The location of the apartment is great - in the heart of the Beyoglu neighbourhood. Lots of cafes, restaurants, coffee shops, souvenir and clothing shops are located nearby in 2-3 mins walking. The view from the window is magnificent - straight at the Galata tower!
The interior of the apartment is beautiful. Some books, statues, several Edison lamps make this apartment lofty and cozy. The apartment was perfectly clean and equipped with all the necessary items: towels, a fan, an iron and a desk for it, a refrigerator. Also, there was a small kitchen and all the necessary items for it, so you can cook by yourself, if you want to.
Eyüp is a very kind and helpful person! The communication was super smooth and quick. All my messages were replied in 3-5 minutes! Also, Eyüp recommended us several nice places to visit and to eat. He also did some extra stuff. I'm sure that not all hosts would do this. For example, he left us some snacks at the apartment, helped us to get our luggage up and down, and allowed us to leave our luggage in the last day in the apartment, so we could spend last several hours walking through the city without our luggage.
Small note that must be considered, if you travel with luggage: the apartment is located at the top floor and there is no elevator. There is only spiral stairs, since the building is probably old. So, it may be difficult for elderly people or people, who have problems with breath, such as asthma, for example, to get the luggage up. But, I am sure that Eyup will help you to resolve all possible inconveniences!
Also, you should consider that it can be a bit noisy because of the appartment being located next to the touristic place and because of the azan sounding from the nearby mosque in the morning.
Summary: Absolutely recommended apartment to explore Istanbul. We could not imagine anything better. Thank you very much, Eyüp!