Showing Classes list instead Course list under Courses field in Class settings.

Canyasa
Forums
Hi guys, I was trying to add a field on registration to enable to select classes, and I added existing field which was "Entity Reference: opigno_class_courses (Courses)" and named Store. After that I realized under class settings Course field showing me classes instead courses. So I decided to delete that field from Account settings. Now at the top bar, under Configuration >People> Account settings > Manage fields > Store still shows and when I try to go there it is giving me this error "Access denied. You are not authorized to access this page." . And also under class settings Course field still showing me class list instead Course list. Please help, how am I going to fix that? Btw I have the admin account.
Canyasa

Update

After deletion of custom fields, I ran Cron, logged out and logged in. Cutom fields are gone now which is ok, but still shows classes under Course field on class settings. And when I try to create a new class (with admin account) I am having this error "Can't save entity as group, because user administrator can't be subscribed to group and become a manager"
Canyasa

I had to delete all the

I had to delete all the database and re-install drupal :/