You should go to iCloud to see if your lost files are backed up previously or restore the files from the backup if you have one. If there is neither, then it's a pity that the files are all gone away and you have no chance to recover them back.
Take care~
About how to run Disk Utility First Aid to repair disks and how to run First Aid from recovery on Mac. What to do when Disk Utility First Aid failed.
Should you use APFS or APFS Encrypted? This post explains their differences, APFS Encrypted vs FileVault and the steps to erase an APFS ENcrytped drive on Mac.