I stayed in Basak's apartment for 4 months during my exchange in Istanbul and enjoyed it very much both before, under and after my stay. Basak answered all my questions (even the most stupid ones you have as a first time traveller in Istanbul) pre arrival. Furthermore she created a WhatsApp group with my flatmates before my arrival in Istanbul, so we could get to know each other. It helped me a lot that both of the girls turned out to have turkish roots, which was helpful in a pre-arrival time.
When I arrived in Istanbul, Basak waited for me in the apartment. She had sent me a document over e-mail with details to find the apartment, which was easy to follow as a first time visitor. She took her time to great me in person and explain about the apartment, turkish culture and how I could satisfy my daily needs when it comes to groceries and etc.
A week after my departure she arranged a dinner meeting with my flatmates + the people from her two other apartments in Istanbul. It was great starter event, where I easily gathered my first contacts in Istanbul. She herself was presented in a great mood introducing turkish food, Raki and bringing stories from her life i Turkey. She even invited me to her home in the South of Turkey if I needed to relax from Istanbul's busy atmosphere.
During my stay she always replied quickly when I had problems with in adopting the differences between the danish and turkish society. She applied me with a new chair when my old one broke and helped me find extra necesary stuff for my room and etc.
Over all I enjoyed my stay at Basak's very much. She is kind, helpful and trustworthy. If you have the possibility to stay in one of Basak's apartment you should find yourself lucky and don't hesitate to book it.
Bonus info: Besiktas is a great neighborhood as a foreign visitor from Europe. It's liberal and I never had problems and I could pretty much continue my usual habits and behaviour from my daily life in Copenhagen, Denmark.