Hi Mauro,
Just change the code like this
add_filter( 'woocommerce_get_price_html', 'custom_price_suffix', 100, 2 );
function custom_price_suffix( $price, $product ) {
$price = $price . '<a href="your_link_here">zzgl. Versandkosten</a>';
return apply_filters( 'woocommerce_get_price', $price );
}