(Folks have already mentioned Odersky and Grossman for grokking functional programming)

FutureLearn has an introductory Dutch course. I've only learned languages from the Romance family previously, so it was a worthwhile experience. (Dutch-Australian in-laws) It's a taster course requiring further study but well worth satisfying your curiosity.

Dutch (and Frisian) may provide a stepping stone to understanding Old English - there are recognisably 'Germanic' traits.