I have dyslexia and in high school learning my lines for plays was really hard but I loved doing plays, so I recorded myself saying my lines on tape (yah, I'm old) and used double cassette to fill 2 tapes with them, then run them over night while I was sleeping. I've never used this in my adult life but it worked pretty well for my lines and I suppose maybe you could use it to learn a language?

Edit: Claude tells me I was a head of my time, apparently it works but not net new, you have to also be working on it awake, it's called 'targeted memory reactivation (TMR)": https://pmc.ncbi.nlm.nih.gov/articles/PMC12592824/