First of all Mehmet is a wonderful man, you're definitely in good hands with him. He's very nice, polite and well mannered. The apartment is nice and compact. You could notice a woody smell when you don't open the windows especially at the beginning but that was okay for me nevertheless if you're allergic you should be aware of it.
Most importantly the place is close to Istiklal Avenue and other attractions are easy accessible from there (Ömer Hayyam).
I would suggest to take a taxi as I found it the easiest and most comfortable way to reach the places I wanted to go rather than public transportation. Make sure to not accept those with taximeter but agree on a fixed price (The app BiTaksi is helpful here to tell you how much your ride should cost).
More advices for your stay:
• NEVER EVER reply to strangers who randomly talk to you on the street and actually seem to be very nice and attractive. They're scammers and criminal. Just pass with a poker face and don't reply AT ALL.
• Never buy something at the first price in Bazaar shops. The price is usually about 30-50% higher than the actual price. Read an article about "How to bargain". It's a game so treat it like it. The easiest way to get the price down is simply to never show you're really interested (poker face) and walk away. Every time you want to walk away they'll tell you a lower price. Always think about what the product is worth to you. What YOU would pay for it and try to get the price down there. It's fun to win haha.