Replacing String in Shortcode

I have a few issues with a plugin I’m working with (businessdirectoryplugin.com) with it’s translation.

I’m having a multilanguage site and the plugin has some issues with certain links with the translation.

For example, on the button “Annuaire” (see link to the page) it always redirects to /de/suche/, that’s correct for the german version, but for french it should be /fr/cherche and for italian /it/cerca.

I came up with the idea, that I could replace the concerned strings on the specific translated pages where this issue is present and added this code to myfunctions.php for the french post:

add_filter('the_content', 'filter_post_479');
function filter_post_479($content){
	if ( is_singular() && in_the_loop() && is_main_query() ) { 
      global $post;
      if ($post->ID == 479){ // 479 is post/page ID you have found
         $string = "de/suche"; //your string to be replaced
         $replace = "fr/cherche";
         $content = str_replace( $string, $replace, $content );
   }
   }
   return $content;
}

Unfortunately, that didn’t work.
I think because the plugin is loaded into the site via shortcode, and so the filter the_content doesn’t apply there.

The contents post is as following:

<h1>Annuaire</h1>
[businessdirectory]

Can someone help me out, how I can replace these strings inside of the shortcode or if there is a better way to do this task?

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