The airbnb was great!
We stayed at the flat for 5 days and it checked all the boxes. The location allows you to walk to the centre of Kadikoy easily, as well as being well connected to public transport. It is about a 20 minute walk to get to the ferries that take you to the European side of Istanbul. If you only want to see the sites then I would consider staying at the European side - just considering the time you'll spend on getting places. Yet we really loved our daily boat rides! Buying tea or salep on the boat was always a treat. Kadikoy is a great neighbourhood, very young and I feel embodies the term "hipster" in the best possible way.
The flat itself is great and we were pleasantly surprised to see that it is bigger than what we expected. Communication with Deniz and with his assistant Gamze was flawless, they didn't have any problem with my slow response rate and offered to help us with anything we might need. They kindly left water in the fridge, and given we forgot to buy it on our way to the accommodation from the airport, saved us a late night trip to search for liquids (the gap water is no good).
Overall I can definitely recommend staying at Deniz's place!!!