Istanbul in 2 days
Assuming that you will be in Istanbul for only two days and here is your list to enjoy your visit

Two days are short but I also had times that I had few days to see city or short weekend trips.
So here is my recommendations for a two day trip. You will get tired but I'll definetely worth it. Please choose comfortable shoes as this trip will require around 20K steps :)
You better get online tickets before you arrive , It can save you a lot of time speacially on top session.
-Day 1-
Choose any accomodation near Eminönü. As most of the hotels will accept your checkin around 13:00 , you can check reviews and enjoy Turkish breakfast around and increase your energy levels. Since It may take additional time to visit my recommended resturants, you can just check google reviews for nearby restaurants and pick one . Ask for a Turkish breakfast with "Menemen" for two . You better finish it in an hour and get your Turkish coffee (with mild sugar / no sugar) and head to Sultanahmet . Visit Hagia Sophia , Topkapı Palace , Sultan Ahmet and obelisks . You can spend 3 hours there .
Just after you finish walk to Basilica Cistern and see there . It will take 30-45mins if you have a online ticket. If you are hungry you can eat meatballs at "Sultanahmet Köftecisi" nearby
Walk uphill to one of Kapalı Çarşı's (Grand Bazaar) gate at Beyazıt square. Take a walk in grand bazar downhill. Follow main ( wide) streets and follow Mısır Çarşısı (Spice/Eygptian Bazaar Signs) It will take you to spice bazaar and you can walk through it. Once you reach to seashore walk over Galata Bridge and you will arrive at Karaköy. You can try Turkish Baklava at Gulluoğlu or Kocak Baklava. Then take the finicular tram to Taksim.
Walk through Taksim street visit have a look at Çiçek Pazarı .
You can eat kokorec and Mussels at Şampiyon or Mercan near çicek Pazarı.
Once you arrive Taksim square you have two options you can walk downhill to Beşiktaş (35 mins ) and see Dolmabahçe palace in middle. or you can use Taksim/Beşiktaş Dolmuş (midibus) or taxi to direclty goto Beşkitaş (7 mins) . I would personelly skip Dolmabahçe palace and head straight up to Beşiktaş. If you choose midibus to Beşiktaş walk to Ortaköy, if you choose Taxi ask driver to take you directly to Ortaköy instead of Beşiktaş.
Once you arrive Ortaköy give a little break there and you can try Kumpir or Waffle. Drink tea near Bosphorus and walk to Bebek.
It should be around 06:00-07:00 pm .I would recommend either Turkish Hamam (Bath) experience) then afterwards a light dinner or reserve Nomads for a fine dining spot or visit one of the roof tops in Taksim square and a good rest for the rest of the night.
-Day 2-
I have two good options for you.
You can have your breakfast on a tour ferry by making a reservation https://lvmrezervasyon.com/
This is good if you wanna see whole bosphorus while you are having your breakfast . :)
or
Get a gözleme or Börek for breakfast. Then go to Eminönü with tram or walking through same route Grand Bazar- Spice Bazaar .Take the ferry to Kadıköy which you will cruise on Bosphorus . Once you arrive kadıköy walk straight up to Boğa heykeli them to Moda . Enjoy your tea or Turkish coffee there then walk downhill to Kadıköy Balik pazari . If you feel hungry there are lots of good choices inlcuding bars and taverns and you can select from my "What to eat" page.
If not take Dolmuş middle bus to Bagdat Caddesi and ask driver to drop you at Suadiye . Once you get off the dolmuş . Walk oppositte direction of Sea and you will find Bagdat caddesi most popular cozy avenue. Walk through Bagdat street and you can also have lunch there.
Once you feel tired take Dolmuş again to Kadıköy and you can enjoy a Turkish Tavern or pub there . But leave Kadıköy around 10:00pm to catch last ferry to Eminönü.
If you want to do some shopping instead of going back to Kadıköy you can use tram that will take you to Eminönü directly and you can shop in Grand bazaar or Spice bazaar.
I hope you will enjoy your two days in Istanbul. Feel free to reach me out if you have an questions :)
