Reham,
Try the fix suggested above - https://moodle.org/mod/forum/discuss.php?d=349351#p1433791 - about changing the dbcollation value in config.php. I had almost given up on running Moodle 3.5 on a shared server since most suggestions required changing global settings that cannot be done. This simple fix was all it took.
It would be great if the Moodle install/upgrade documentation included information about this fix. I'm sure there are a lot of Moodle installations running on shared servers by those who do not have the option to move to a more expensive dedicated server environment. I hope the Moodle developers don't forget about this group of users.