Right, you will have to learn the standard written German, that the Germans pronounce very differently according to the region where they come from - this standard or Hochdeutsch is "spiced up" with a lot of dialect words added and pronounced somewhat differently from what the written version. It can be quite hard to understand especially the Bavarian dialect (although the Bavarians will always understand you speaking standard "high" German), with the Swiss German the case is even worse, which I (being a German teacher myself) cannot really understand without difficulty. Also some people will make fun of you, speaking strong dialect to make you look stupid. Yes, there is something called "German humor" ! Don´t worry: Ask them politely to speak slower and they will, after some months you will be OK !