custom field search query

Hello I need help with your plugin.

before, a really nice plugin – I like it and buy the startup.

i have put in a custom field named Ortschaften ..

function search_by_ortschaften_form_load( $form ) {
    
    if( $form['name'] != 'search' ) {
        return $form;
    }
    $form['field'][] = array(
        "name" => "ortschaften",
        "type" => "adverts_field_select",
        "order" => 20,
        "label" => __("", "adverts"),
        "max_choices" => 10,
        "options" => array(
            array("value"=>"Aarwangen", "text"=>"Aarwangen"),
			array("value"=>"Bützberg", "text"=>"Bützberg"),
            array("value"=>"Eriswil", "text"=>"Eriswil"),
			array("value"=>"Herzogenbuchsee", "text"=>"Herzogenbuchsee"),
			array("value"=>"Huttwil", "text"=>"Huttwil"),
			array("value"=>"Kleindietwil", "text"=>"Kleindietwil"),
			array("value"=>"Langenthal", "text"=>"Langenthal"),
			array("value"=>"Leimiswil", "text"=>"Leimiswil"),
			array("value"=>"Lotzwil", "text"=>"Lotzwil"),
			array("value"=>"Madiswil", "text"=>"Madiswil"),
			array("value"=>"Murgenthal", "text"=>"Murgenthal"),
			array("value"=>"Roggwil", "text"=>"Roggwil"),
			array("value"=>"Rohrbach", "text"=>"Rohrbach"),
			array("value"=>"St. Urban", "text"=>"St. Urban"),
			array("value"=>"Wynau", "text"=>"Wynau"),
			array("value"=>"Wyssachen", "text"=>"Wyssachen"),
        ),
        "options_callback" => "",
        "meta" => array(
            "search_group" => "visible",
            "search_type" => "half" 
        )
    );
    return $form;
}

How must be the query for Search?

I have a code, but its for taxonomies..

add_filter( 'adverts_list_query', 'search_by_ortschaften_query' );
/**
 * Adds tax_query param to WP_Query
 * 
 * The tax_query is added only if it is in $_GET['advert_category']
 * 
 * @param array $args WP_Query args
 * @return array Modified WP_Query args
 */
function search_by_ortschaften_query( $args ) {
    
    if( ! adverts_request( "ortschaften" ) ) {
        return $args;
    }
    
    $args["tax_query"] = array(
        array(
            'taxonomy' => 'ortschaften',
            'field'    => 'ortschaften',
            'terms'    => adverts_request( "ortschaften" ),
        ),
    );
    
    return $args;
}

Can you help?