I can give the highest score to the apartment and Zeynep as a host.
1. Location. The location is perfect - close to Istiklal, Galata Tower, Şişhane metro station, tram stop, and ferry station (karaköy). Lots of coffee shops, restaurants, and vintage stores around.
2. Apartment. The apartment is very cozy and has an excellent view over Istanbul. The apartment is very quiet despite the fact that the apartment is in a busy area. The apartment has everything you need for a long stay (except iron) - stove, cooking utensils, and coffee maker.
And the large and comfortable bed we just fell in love with.
3. Interaction with the host. Zeynep is very friendly and responsive - she was always quick to answer questions that arose and showed participation and care. We did not have any problems during our stay.
Verdict: we would love to come back to this apartment again)