Welcome.
Few important questions I have for you:

- Where did you collect all the information and questions used for quiz in your app?
- Is your app open source or not, and if it is open source please post github link for checking and inspection.
- What exactly are you selling in app?

Somehow I doubt people today have enough patience to spend one hour solving a quiz to get certificate, and it would be much better done in stages.
People also love visual stuff and videos, and some short Bitcoin educational videos would be nice to have.