Agreed. I'm decent with languages (native English speaker, C1 German, B2 French, B1 Mandarin and Spanish, can fake my way through common travel situations in M

Agreed. I'm decent with languages (native English speaker, C1 German, B2 French, B1 Mandarin and Spanish, can fake my way through common travel situations in Moroccan Arabic and a couple other African languages). C1 in 5 months sounds wildly optimistic, even with immersion. I wouldn't consider myself to possess C1 French despite a couple years of classes in school and maybe a year of immersion broken into a few chunks. My German fluency came from ~10 years of classes, including several college classes in other subjects that were taught in German. For that matter, I know non-native english speakers who don't have C1 fluency despite living in the US and UK for more than 20 years, and not for lack of trying. Learning languages is hard for almost everyone, and for a reasonable portion of the population, it's really hard.