Obviously, the Germans speak a language all of their own. In fact its a very humiliating thing for Austrians (and some Swiss) that they speak German, and they don't even have the excuse of coming from Germany!
When i first went to Germany (in 1988, to watch Englands European campaign) i knew only 2 phrases of German: "Ein Bier" and "Noch Eins", which translate as "One beer" and "another one" and that saw me through 2 weeks OK.
But of course the more you know, the better you will be able to enjoy a visit. Of course most phrases we learn from old films, like "Hande Hoch" and "Donner und Blitzen" are of limited use, although shouting "Schnell! Schnell!" at the match normally goes down OK (but not in the bratwurst queue)
As regards football phrases, here are some useful ones to learn for use in Germany (thanks to The Guardian for this list)
Aufzugsmannschaft or Fahrstuhlmannschaft ("elevator/lift team") - a yoyo-team (i.e. one that keeps getting promoted and relegated).
Anschlusstreffer - the goal that reduces the deficit to one (eg brings the score to 2-1 rather than 2-0).
Angstgegner ("fear-opponent") - a bogey team.
Bauerntrick ("farmer's trick") - the Cruyff turn.
Bauernspitz ('farmer's point') - like the Danish toe-howler, an oafish kick with the tip of the boot.
Blutgraetsche ('blood straddle' ) - sliding tackle that goes through the opposing player.
Ehrentreffer ("honour strike") - consolation goal, also referred to as ergebniskosmetik ("result cosmetics").
Englische Woche ("English week") - a week in which a team plays both at the weekend and in midweek.
Gurkerl ("gherkin") - nutmeg (in Austria).
Kerze ("candle") - a bad attempted clearance whereby the ball is whacked straight up in the air (like the Dutch 'rocket', then).
Notbremse ("emergency brake") - professional foul; when the last defender or the goalkeeper brings down a forward to prevent an almost certain goal.
Rote Laterne ( 'red lantern') - the team at the bottom of the league (this theme is also found in France, where the basement-dwellers are known as 'la lanterne rouge'; in both countries, the last carriage on a train has a red light at the back).
Schwalbe ("swallow", as in the bird) - blatant dive (also used in Dutch). Den sterbenden Schwan machen ("to do the dying swan") is also very common.
Tunneln - to do a nutmeg.
Wembleytor ("Wembley goal") - A 'goal' that is awarded even though the ball didn't cross the line. No hard feeelings over 1966, then!