hide shipping method ID

gistfile.php

add_filter( 'woocommerce_package_rates', 'hide_shipping_methods_based_on_item_count', 10, 2 );
function hide_shipping_methods_based_on_item_count( $rates, $package ) {
    // HERE the targeted shipping method ID (see the attribute "value" of the related shipping method input field)
    $targeted_method_id = 'flat_rate:12'; // <== Replace with your DHL shipping method ID

    // HERE the articles count threshold
    $more_than = 15;

    // Cart items count
    $item_count = WC()->cart->get_cart_contents_count();
    if( WC()->cart->get_cart_contents_count() > $more_than ) {
        foreach ( $rates as $rate_key => $rate ) {
            if ( $rate->id != $targeted_method_id ) {
                unset($rates[$rate_key]);
            }
        }
    }

    return $rates;
}