Way too little time in Berlin.
I'd actually skip the Reichstag dome, the lines are really long. Stick to the Mitte, if you're not too willing to walk around much, the day transit pass is a good deal.
I like the East Side Gallery part of the wall, you also get a flavor of the former East by walking around Alexanderplatz. Get some lunch in the various cheap eateries nearby, head to the Pergamon Museum to see the Ishtar Gate and the Roman marketplace, then make your way slowly to the Brandenburg Gate, the Holocaust memorial, and the Reichstag.
Finish your day with a bit of the Ku'damm and the memorial church, maybe a quick tour around Potsdamer Platz or a drink in Kreuzberg or Schoeneberg.