Because this thread is asking for questions for a video, I've moved this to the script/video ideas/planning forum. ^^
I've had a lot of Spanish classes, and quite a few German classes. I tried to teach myself some Korean in my free time, although my pronunciation is pretty terrible.
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I've forgotten most of the languages I've learned bits and pieces of. =(
Some common difficulties would be false cognates. Lots of Germans become objects in English, and English speakers receive professions in German.
bekommen in German = to receive
become in English = to come to be
Then we have funsies with spelling. English spells it "Kaput," German spells it "Kaputt." x_x
Umlauts are hard for English speakers unless you know where your tongue is supposed to go. Once a person learns the tongue is supposed to stay in the same place as it is when you say the "eeeeeee" sound (as in "creek"), then the letters become much easier to pronounce. ^^ Also the ch in English is really different than the ch in German.