Unfortunately, I had a very unpleasant experience here.
First problem: the noise situation is unbearable. There is a large construction project directly beside Kerim's building. The workers there told me it will be an active construction site for most of 2021. Apparently, they are tearing down a 5-storey building and putting up a new one.
Then, there were renovation projects in the apartment directly above Kerim's. The owners of that apartment were tearing out the walls and replacing the floors and often worked till late at night.
To compound all this, Kerim's apartment directly faces one of the busiest avenues in Istanbul so it might be difficult to get good sleep since the windows are not sound-proofed.
Kerim assured me prior to booking that there would be no noise issues. It was only after I checked in that he admitted he knew about the noise problems, but he told me that if it bothered me so much I could always go back to my country.
Second problem: Kerim was reluctant to give me access to his wi-fi.
The password details in the listing had been deactivated when I arrived and could not be used. After calling Kerim from a hotel to obtain the correct wi-fi details, he initially suggested that I just use the hotel's wi-fi since I was already there. It was not until a staff at the hotel pleaded on my behalf that Kerim finally agreed to send the log-in details but even so, I had to wait for almost two hours before he sent them.
While Kerim's listing is nice (the modern furniture and use of space are appealing), I feel Kerim can become a better host by doing 2 things: 1) be upfront with all guests about the noise situation 2) remember to treat people how you yourself would like to be treated no matter their background. :-)