Its a problem with hosting permission that the component can not replace/move file while installing.
Can I take a look your hosting info to check?
“Futhermore, I can not see the pages made with Quix”
Quix uninstalled before that why you cant see the page built with quix, the solution is reinstall quix but we’re facing the issue with permission.
For this case, could you please enable ftp account via joomla configuration then try to reinstall the quix again ?
Add the ftp account then install the component with your ftp account permission.
If you still face the issue with installing package, please open a ticket here https://warptheme.com/member-area/ticket-system/