Visiting Berlin 17-20 May, what to see?

Two of us are visiting Berlin in middle May and are looking to spend some good times getting to know the city a little bit and then trying some good local food that is typical for the region. Do you have recommendations? We are from Croatia originally but live in Houston Texas and are coming to pick up our Volvo in Gotheburg, then driving down south to Prague.

Thank you friends, Tajana