URL

Hi,
to hide the “blog” part of the URL you would need to add in your theme functions.php file the code below

add_filter( "adverts_post_type", function( $args ) {
  $args["rewrite"] = array( "slug" => "petites-annonces", "with_front" => false );
  return $args;
} );

Once you add the code go to wp-admin / Settings / Permalinks panel and click “Save Changes” button to reset WP router and apply new URL schemes.

It seems you have send the same message via the contact form as well, so you should receive the same reply via email as well, please do not double post your questions, thanks.