Help with translating a certain French sentence that I'm not quite sure about.
Hello. I am wondering how to say "I wonder what subjects they learned about" in French. I'm sort of confused because I don't know how to say "to learn about" in French. What preposition is used? Also, in this case, what it be necessary to say "que" after "quels" or is that not correct? My attempt would be "Je me demande quels sujets qu'ils ont appris", but that seems wrong. A lot of things can come up with "discours indirect" that have simply never been said by me, and that can cause problems, but I use it a lot in French, and thus, I intend to completely master it. Thank you very much for helping me with this translation.