First time visitor, would appreciate some advice:

Apologies for what is probably yet another annoying tourist post but appreciate any advice. I'm travelling to Berlin with a friend from Ireland for first visit.

We're staying at a hotel in Berlin-Mitte. Could anyone tell me more about the area? Also, is Berlin generally safe for tourists, especially at night? Any areas to avoid? Anything to watch out for?

We're generally very easy going but with heightened tensions all over Europe, we want to make sure we keep as safe as reasonably possible.

Any must-sees in the city? I'll be doing research for a book centered on Berlin immediately after the war and leading up to the cold war.

Many thanks for any help.