Went recently and enjoyed bars in Kreuzberg - sort of anti-fascist Bohemian part.
Felt very quiet compared to other busy cities but as above post recommend a WW2 walking tour. Wasn’t fussed about Checkpoint Charlie and Brandenburg Gate but some good free museums. Topography of Terror if you want a reminder of how evil the Nazis were. Also some interesting stuff about the wall.
Season finished but football is a different level there in terms of experience of the day with thousands there two hours before game drinking etc.
Transport easy to get around on trains, didn’t try the trams, although Ubers were very cheap too.