You can change the add listing login message from the GD > Add Listing block or shortcode. The message shown after a listing is submitted needs either a translation of that one string or a small code snippet.

The “You must login to post.” message

Logged out visitors see this message on the add listing page. The GD > Add Listing block has a Login Message setting in its Login group. Type your own text there and update the page.

If your add listing page uses the shortcode, add the login_msg attribute:

[gd_add_listing login_msg="Please create an account below to get started."]

The same Login group has a “Show the login and register links if required” option, so visitors who have no account yet get a link to register.

The “Post received, your listing may need to be reviewed” message

GeoDirectory shows this after a new listing is saved with a status other than published, for example when new listings are set to pending review. When an edit to an existing listing is not live yet, users see “Update received, your changes may need to be reviewed before going live.” instead.

To change only the wording, translate that one string in the GeoDirectory core plugin. How to change just one language string walks through it with Loco Translate.

If you would rather use code, the geodir_ajax_save_post_message filter lets you replace the message. This snippet changes it only for new listings that still need review:

add_filter( 'geodir_ajax_save_post_message', 'my_gd_review_message', 10, 2 );
function my_gd_review_message( $message, $post_data ) {
	$is_new  = empty( $post_data['post_parent'] );
	$is_live = in_array( $post_data['post_status'], geodir_get_publish_statuses( $post_data ) );

	if ( $is_new && ! $is_live ) {
		$message = 'Thanks! Your listing will need to be reviewed before it goes live.';
	}

	return $message;
}

Add it with the Code Snippets plugin or your child theme’s functions.php. Your text replaces the whole message, including the preview link, so add one back if you want it.