Glad that OP is aware of potential language difficulties if the coursework is not in English. I have two acquaintances with dual citizen children, US and Germany. Both sets of kids speak German fluently (language spoken at home), read fluently and studied German to AP levels and in extra curricular classes. All attended a very demanding US high school where they did well. All passed uni required German language evaluative test (like the TOFEL for foreign students studying in the US) with highest marks. Kids studied/study at several different German unis. All found that their written German for the papers required in their coursework was not at the level expected by their uni profs.