Our Single listing pages are Custom Post Type “acadp_listings” and they cannot be found under “WordPress => Pages”. Normally the layout for posts is controlled by single.php of your theme. Since ACADP listings are Custom Post Type “acadp_listings”, they will use the same post template (single.php). So, you can Override the single post template (single.php) from your theme, like “single-acadp_listings.php” and do your changes inside this file. Kindly refer https://developer.wordpress.org/themes/basics/template-hierarchy/#single-post
And you need to contact your theme support team to add/remove the sidebar and navigation.
But, if you just want to alter the listing content displayed, then you will need to override our listing detail page template. Kindly refer
https://pluginsware.com/documentation/customizing-acadp-templates/
You will have to override the /wp-content/plugins/advanced-classifieds-and-directory-pro/public/partials/listing/acadp-public-listing-display.php file