Please confirm the permission for plugins deactivation, and switch to the parent/default theme. As soon as we complete the testing we will enable all back, You would better make the full backup of your site. Also, send me the admin access to the dashboard panel.
I think the demo import failed because of PHP settings. Can you import all files again so everything works perfect?
I think some other features are also little bit broken. Can you re-import all demo files? Do not replace any content.