Need a design for mobile App

The App would allow for teacher's to publish interactive books that would serve as small language courses. For now I am only interested in the design for the student, the UI for the teacher will be a different App.

Here are some of the structure of the books.

- A book contains :
* A title
* Some intro (Optional)
* An Index for student to navigates its content
* Units

- A unit contains:
* A Title
* Some intro (Optional)
* Lessons

- A Lessons contains:
* A title
* Vocabularies (students can play to listen for each word's pronunciation, students can also pronounce each
* word and the app will use speech recognition and give feedback)
* Article (students can listen and read)
* Media content (Audio, Video)
* Exercises (unscramble, true or false, complete, image or video)

Here's an example of an App that does something similar: https://apps.apple.com/us/app/duolingo-language-lessons/id570060128