Hello dear Thank you so much and yes i will write you some places you must visit in Istanbul but how many days you will stay there?
First the most important place to visit is Haghi sophia Museum, Topkapi palace( The sultans home) and sultan ahmet mosque they are all in one place it’s called sultanahmet and also you can sea the History museum and also the Roman and pharaoh obelisk also in same area.
Also you can visit dolmabahce palace in kabataş on the sea side and when you finish from this Palace you can take A bosphorus tour near the entrance you can ask anyone and they will help you. Always ask the local people the shops. DON’T ASK THE TOURISTS.
FOR THE FOOD YOU MUST EAT the lahmacun meat on the bread makes in oven and Manti, Dolma and for sure the most delicious and important thing Kunafa you can find it everyevery 
Am here always if you want any help
Best wishes.