Sidebar not working

I still have a problem with the sidebar not working. I wonder if I need to choose a different course-platform or change the Theme (-> create the entire website again).
I need to have a first version working until Thursday.

Adrian, the Theme developer (Total Theme) has given me this  snippet and it is active:

Course ID is “course” and the CSS code from the instructions (https://lifterlms.com/docs/lifterlms-sidebar-support/) has been integrated.

// Alter the layout for the courses post type
// Choices: left-sidebar, right-sidebar, full-width or full-screen
add_action( ‘wpex_post_layout_class’, function() {
if ( is_singular( ‘course’) ) {
$layout = ‘right-sidebar’;
}
return $layout;
}, 40 );

The orignal LifterLMS example does not work correctly https://deepdialog.de/kurs/lifterlms-quickstart-course/

and the same problem is with my own course page https://deepdialog.de/kurs/knotenknacker-paket/

What can I do?

Thanks for your support,

Ulf

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