Viel Glück! :)
German is a real mess. Well it helps if you know a little bit of English, since both languages derived from the same language family, but it gets complicated as soon as you have to deal with all of these (mostly stupid) exceptions the language has. In fact many germans seem to have problems using their own language properly because of all the exceptions. Well, no, some of them don't even get the basics done xD
Also maybe it's just me, but every time I notice someone mixing up different languages I'd like to punch him in the face. I know they want to sound cool and other languages are always cooler than the one you grew up with, but is it really necessary to put words like "kawaii" into a sentence that doesn't consist of japanese words?
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Well, since I took the time to post I might as well join. My native language is German and I also like English really much. I also studied Latin in school for six years (even though I guess I've already forgotten most of the stuff; haven't used it in ages xD). Depending on if computers and stuff like Java, C++, etc. also count I could easily append my list of languages but I guess that would get a little too far xD
My tool of choice is practice or to be more precise: I like watching videos (Let's Plays and stuff). It's difficult at first but you get used to it and if there's a word I don't understand I simply google it xD
Also if I really want to get into a language (mostly programming languages) the internet has a large amount of tutorials, so there's no specific source or tool; at least for me