There's a couple of ways but I'll explain the most direct.
On the top line of the PS4 menu
Settings / Application Saved Data Management / Saved Data in System Storage / Delete / Project Cars 3 /
You'll then see a long list of files. Press the options button on the controller and select sort by name - this should clump the ghost files together. Now you can now select each file individually and multi delete them.
But there are 4 files you
NEED to keep and hopefully they should be at the top after the sort - the career save and the profile save, plus both their backups. At the bottom of the list are any tuning/setup files you may have made so it's best to keep these as well.
** It's always a good idea to back anything up before you start "messing" either online if you have PSPlus or to a usb memory stick if you've got one. Actually it's a good idea to back files up regularly anyway. And you can do this from within this menu.
Right, I think that's it.
