OneNote
OneNote is a digital note-taking app that provides a single place for keeping all of your notes, research, plans, and information. It’s available in Android, IOS and Windows devices.
Forest
Forest is a popular productivity app that helps people beat their phone addiction and manage their time in an interesting and pleasant way.
Penly
With Penly, you can easily digital plan or take digital notes using its tools and features. It can be purchased on Play Store for 6,49€.
Quizlet
Quizlet is a study tool based mostly on flash card- and quiz-style recall of facts. Users can create and then test themselves on study sets they create.