Quizlet is also a good app for revision. I found that really helped me with Latin which was partly memorising poems and stories in bitesized chunks and it really helped me break it down. Also some schools and teachers make up flashcards on quizlet and put them on there so I used some of those for biology. It also allows you to make the information you've put in into a test so you can see how you're doing. Would really recommend it!
If you think you're someone who learns by hearing, you might want to record yourself using the microphone or voice memo on your phone. I know this helped for a few of my friends doing French, especially for their speaking.
Honestly it just depends on what type of learner you are and how you best remember information. Those are just the kinds of apps that I found useful and I'm a very visual learner so I spent a lot of my time making flashcards, watching videos, drawing diagrams and writing notes etc and sticking them on my wall. I only really used quizlet for Latin and biology. Hope this helps!