Trust credentials from google

Using /e/OS Settings
6

In the official documentation, about TWRP :

  1. Go back to return to main menu, then tap Wipe.
  2. Now tap Format Data and continue with the formatting process. This will remove encryption as well as delete all files stored on the internal storage.

Missing step : reboot to recovery

  1. Return to the previous menu and tap Advanced Wipe.
  2. Select the Cache and System partitions to be wiped and then Swipe to Wipe.

You already have TWRP installed, so in my how to, Go directly to step 7) or 8)