In summary, the view from Aygen's place is absolutely beautiful, the apartment is spacious and really well located and Aygen is a really warm and helpful host. I would highly recommend you stay here.
PROS:
Located 5 min walk from Galata and surrounded by great cafes.
Mesmerizing sunset views in backdrop of the old city.
Big spacious apartment with 3 double beds.
Elevator! Many airbnbs in this area are good but are only walk ups. this one has an elevator (although entrance requires few steps - no big deal)
CONS:
The floor in the building creaks so it may not be best suited for super noise sensitive sleepers.
The second bathroom is very tiny, although it includes a shower area. (this is not really a con, but just a heads up)
Overall, would highly recommend staying here :)