I will be in Istanbul for 2 days in October. Any recommendations?

Hi,
Welcome to Turkey. I live in Istanbul and I can tell you that Istanbul is the best city In the world.
Here is some advice for you to visit:
1-Kadikoy. Kadikoy is in the asian side Istanbul and you can meet the local Istanbul people over there. You can just meet the tourists at the other places who comes from different cities or countries. So, Kadikoy the place you should really walk around.
I know you have no time (only 2 days) but it's necessary
2-You said that your hotel will be in Fatih. So, you can easily visit the grand bazaar. You can find historical things in there. (You should get a map, so you will not get lost)
3- If you really like the historical places, you should visit one of the oldest Church in the world which called Aghia Sophia. (It was a cathedral, then Turkish people came to Istanbul and we covered it as a mosque. Then Turkish government made it a museum. etc.. you can read about it on wikipedia).
4- Taksim, Beyoglu. Just walk around in there and see how amazing the architecture.
5- Take a Bosphorus Tour (long one) (you should really do it)

I think it's enough for 2 days. I wish I was in Turkey and help you more.

Have a nice trip and you can ask me questions any time about anything.
Have fun,
Stay well.