Highly recommended in case you're looking for an apartment for a short term trip to Istanbul. We lived in the apartment with 2 persons. I would not recommend this flat for more than 2 people because the bathroom will be too small for you in this case. But thats just my impression.
It is located right in the heart of Besiktas which we really loved. You'll find anything you need by walking 5-10 minutes.
At times the WiFi tends to be a bit poor, but since there are dozens of Coffee Shops right around the corner, I tried lots of them for working remotely. In my mind O Coffee (just 1 minute away) is the best (in terms of WiFi & Coffee).
I would book with Göksen again when visiting Istanbul in the future.