WPSchoolPress broke part of my school website

My dashboard does not work anymore
can not access backend.

I installed this plugin and i could not access my pages and blogs anymore also my plugins page was not more available to deactivate plugin.

i tried to recover by restore with backup of the wordpress directory.

but still not working. is there a change in the database that makes my pages are not available.

Please help

Kind Regards
Maria Venus
Beauty Academy Eye For You
Website: https://www.beautyonderwijs.nl

The page I need help with: [log in to see the link]