To start over from the very beginning, you can initialize your progress simply by deleting/reinstalling the app.
Please think carefully before proceeding with the game initialization.

If it doesn't work, please try to clear your cached data by referring to the following steps:

[Apple]
1. Go to in-device Settings > General > iPhone Storage.
2. Tap the App - Offload App - Reinstall App

[Android]
1. Go to in-device Settings > Apps > scroll to All apps - scroll down to the “Google Play Store” app.
2. App details - “Clear data” button - "Clear cache".
(Please be aware that the steps can be different)

Hope it helps!