where to stay

Berlin is a large city, if you don't want to uses buses or trams that will mean a lot of walking to get to many sites. No matter where you are staying.

I know Berlin is a large city, we can walk for about 7 hours a day in around the city ( if not more)
..so your best place to stay in...thanks

Mitte is central to a lot of sights and good transportation. I liked this hotel at Hackescher Markt, a block from the S-Bahn (serving the airport and Potsdam) and a few blocks from Alexanderplatz U-Bahn and Museum Island.

In that case my honest opinion is that it really doesn't matter that much where you're staying as long as it is within the Ringbahn. Normally I'd suggest staying close to good access to public transport, but if that is not important you can stay anywhere you like. You'll need to walk far no matter where you end up. But it would be helpful if you told us what you plan to do and see while in Berlin.

Mitte is not a bad option but you can also consider e.g. Friedrichshain, Moabit, Prenzlauer Berg or Tiergarten.

we are planning to go to the Jewish Museum, and other museums..shopping and food tours, Berlin Wall.. would that help you suggest an area...Thanks again

Area around station Friedrichstrasse.

By the way: Moabit and Tiergarten are subdistricts of district Mitte; also a subdistrict with same name. Just to sort all these names of different categories.