So once again we have a "no way to be sure" sentence with multiple (or zero) correct interpretations. Splendid. As a student, I personally would never "study" my (class) notes, though I might "review" them. As a oboe player, on the other hand, I indeed have to "learn" my (musical) notes, but I wouldn't "study" them.
I guess that is something we are missing in Duolingo (But, I say this with the necessary caveat that "one gets what one pays for."), which is context. That is why I think Duolingo's Stories are soo very wonderful! I'm hoping to use them together with "mind mapping" techniques to retain the new words and colloquial expressions they give me. Just need to find the time to find a good mind mapping software . . . to make myself study materials similar to this: https://youtu.be/G2N7zXLpxno