Hi,
WP Customer Area does not show any sidebar on single private contents. This sidebar is probably coming from your theme.
However, WP Customer Area is by default using your theme’s page.php files to render page listings, and your theme’s single.php files to render single content pages.
To fix that, you could for instance copy page.php from your theme to your child-theme, and rename that file to cuar.php.
Then, make your changes into it (for instance, remove the sidebar), and you should get the same appearrence in both pages and posts.
If you want more control over the theme templates structure, please check our theme development documentation. Check section named Custom pages templates and Custom single templates.
Regards.