It's great to hear from your movement! I hope everything goes well with that!
Anyways, i've been to one american convention before (Otakon) and all I can say is: germanys cons are MUCH smaller. Much much muuuch smaller.
We have conventions nearly in all parts of germany. There's one in or nerby munich if I remember right. But I never went there.
Cons which could be interesting for you are: Connichi which takes place in Kassel..so that would be just a few hours away from Munich
It's one of our biggest Cons and usually pretty nice. Connichi or short called "nichi" is my favourite con in germany
Animagic is nice too.. but I don't like it that much. Animagic takes place in Bonn, which is pretty much in the northwest of germany. It's one of the biggest cons, too. (But I don't like it that much because of many reasons)
The bookfair in leipzig is also a popular 'con' where many cosplayers met, even if it's not a 'con'...just a very big bookfair. But cosplayers go there every year.
I like the bookfair because it has a nice location for photo-shootings and I love reading books, not just Manga (well I nearly never read manga *cough*)
People are usually pretty friendly and fun. But of course there are douchebags, too. it's pretty similar to Otakon, for example. (If you ever went there)
it's great that you want to learn the language! it's pretty hard to learn.
I really hope you will feel welcome in germany and like it
If you have any questions, just ask
I'd love to answer and help wherever I can.
(bookfair takes usually place in march.. so this could be the first 'con' you could visit. but it's a long journey from Munich to Leipzig.
Ohh and there's a very small but absolutley lovely con in Ludwigshafen called 'Hanami'. It's really very small but it's great to just hang out with friends and get in contact with a few people. Hanami takes usually place in May.