Well, you seem to at least have everything backed up, so remove everything out of
your 'already attempted' upgraded' DB, upload your Backup Content again into
a CLEANED OUT Shop Directory, (exept for the images, wich could be left in their place).
Then, install the Shop in a regular way onto the virgin DB, an then, restore the saved
DB-Content back onto the DB again.
You could have had it easier, by NOT overwriting an existing Software. It's like copying
a Win-10 Disk Content over an existing XP Directory.
Very very unprofessional, in any case!
Good Luck
Ernie