Recover HDD after flashing

Hello. I did a mistake. For some reason it looks like I flashed my external hard drive for booting. I didn’t want that to happen as all my backup files are in that hard drive. It is now partition of 4,5 GB instead of 4 TB. I used balenaEtcher to flash for installing Parrot.
Is there any chance to recover the original size of the hard drive and files? It would be very important for me to recover the hard drive.

Can I undo the partition and then recover the files/folders?