Berlin is a very colorful and versatile city. What you "need" to see when you are there depends on your interests. We have too much of everything to name five things everybody likes to see. Even stuff like "visit one or two museums". You can visit many museums about history, ancient history just as WW2-stuff or rather go to the Currywurstmuseum or Computerspielmuseum (= Computergames). Or Legoland and the Berlin Dungeon.
Of course there are the basics of the basics like the ones you already named but if you are afraid of heights, a visit on the Fernsehturm or Funkturm won't be something which lightens your day