So the backup .mbz file already resides on server and you are not uploading but merely selecting the backup file at the start of a restore process. So increasing the values in php for uploading files doesn't apply then.
Your server is on shared hosting (OVH) ... which means it has limits/caps - maxes that any application (moodle) cannot go over.
Suggest stepping through the restore and select ONLY the quiz ... by itself ... no other resources in the backup.
Quiz is one of the heaviest to restore as one is restoring a question bank.
If you hit a percentage this time (again) and it fails am venturing an educated guess (without actually seeing this) your server is reaching those limits ... server just stops doing whatever ... no error is reported for it's really not an error.
So ... without upgrading your shared hosting plan, your only alternative might be to reset the course ... and in the options to reset, remove all students in the course and their work/grades, etc. That action resets the course to one that has only resources and ready for you to enroll new students.
For technical reference:
whois [yourserveripaddress]
responds with
netname: OVH
descr: OVH SAS
descr: Shared Hosting Servers
If you do not want to reset the course, then contact OVH hosting an inquire about upgrading your hosted instance to some offering of OVH that can handle what you are trying to do.
'SoS', Ken