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~
This post explains the reasons why your Mac won't boot from the bootable USB drive and covers the solutions to force your Mac to boot from the USB.
Read to know what is SSD TRIM, including the benefits of SSD TRIM command and how to enable SSD TRIM on Mac.