There is also the very handy "Berlin Subway Map" app for working out the routes. If you are able to use mobile data outside the UK without being charged too, it's also worth pairing that up with the "DB Navigator" app for working out when the latest trains are while out and about in Berlin.
Been to Berlin three times in the past two years, including for New Years Eve last year. Love the city. Still loads I've yet to get round to doing including going inside the Reichstag and catching some football. Planning to tick off the latter with a trip in February to go watch Union Berlin...