Few days in Berlin

Hello Berliners,

I'm arriving tomorrow morning to Berlin for the first time :-) will be staying there till Monday so only 4 days to see the city.
Any tips what's a must see, good restaurants, German cuisine to try, anything you can think of really that you think I should see/try.
I will be by myself so if anyone feel like having a coffee/drink/sightseeing with me?

Any help will be much appreciated and I promise to return a favor when you come to Israel :-)
Thanks!
Hilla