Disable ldap authentication

I use the LDAP Integration App for user authentication with my owncloud. It’s working but I don’t want to use it anymore. I would like to change my users with LDAP authentification to normal backend users where I can set the password manually. How do I do that? I won’t let me simply take them out of the group ‘LDAP’ and when I disable the LDAP Integration App, I’m not allowed to change the passwords of the users.

Does anybody know how to convert an LDAP-user to a BACKEND-user?