File vault

It is not entirely clear whether you just have Filevault enabled on the boot drive or whether you also encrypted the external drive as well. If you forget the login password when booting macOS, then you can try resetting the macOS user account password:

https://support.apple.com/en-us/HT202860

If you forgot the password for an external encrypted drive, then you are likely out of luck unless you have a recovery key for it.

You should always have frequent and regular backups of your computer and all external media (including the cloud) which contains important & unique data.

I do not see a question.

Forgetting an encryption password is bad, yes. Unrecoverable-level bad.

Hard drives can and do fail, and can particularly fail under heavy load.

Continuing to use hardware while disregarding warnings tends to not end well.

If you lost administrative access to the Mac, a backup and reinstall can usually recover that. There are other (unsupported) ways, but having admin access drop off and warnings can mean software and/or hardware corruptions.

The FileVault password is usually your login password.

Marking a thread as solved will reduce the number of folks that will read.