Perfect location - close to the busiest shopping street and Galata tower yet super quiet. The apartment is located 1 min from Galata tower and 1 minute from İstiklal Avenue. It's on top of a bakery so no noise at night. The apartment is super clean and seems to be pretty new.
Volkan has been a great host helping us with all our questions and reserving us a taxi on our way back to the bus station.
For first-timers in Istanbul - from the airport catch a Havaist bus to Taksim. It costs 3-4 euros and they depart every half an hour. Don't change money at the airport! We lost ~20% of our money with the bad conversion rate (change somewhere in Taksim square and compare prices). From Taksim, catch a taxi to Galata Tower and Volkan's place. It's 20 min walk from Taksim to the apartment but it's very steep in some places so not easy with luggage. The taxi is like 3-4 euros so walking is not worth it.