App not working Bookmarks neo reader NeoReader

The following describes how to:
1. Force stop an App
2. Clear the App cache, user data remains.
3. Clear the app storage, user data is lost.

The method works for any Android App.

My device is a Nova3 Color, the steps may differ.

Go to Settings Menue.
Tap on the version image.
Tap on the App row.

Or go to the Apps Menue.
Hold down on the App.
Click Manage.

Do a FORCE STOP.

This may already fix the issues.
If not you may proceed.

Click on Storage & cache.
Clear the cache. User data will remain.

This may already fix the issues.
If not you may proceed.

Click on Storage & cache.
Clear the storage. This removes user data.