Wordpress add automatic price update after quantity change on single product page

Question

I am using the Porto Wordpress theme. The problem with that theme is that it does not show an automatically updating product price under the "Add-to-cart"-Button. It only shows the standard price for quantity = 1 below the product name.

I have already tried some solutions, e.g. show price*quantity in single product page

or

function bbloomer_product_price_recalculate() {
   global $product;
   echo '<div id="subtot" style="display:inline-block;">Total: <span></span></div>';
   $price = $product->get_price();
   $currency = get_woocommerce_currency_symbol();
   wc_enqueue_js( "      
      $('[name=quantity]').on('input change', function() { 
         var qty = $(this).val();
         var price = '" . esc_js( $price ) . "';
         var price_string = (price*qty).toFixed(2);
         $('#subtot > span').html('" . esc_js( $currency ) . "'+price_string);
      }).change();
   " );
}

But they do not seem to work. Any solution out there, how to add automatically updating price after quantity change in single product page?

Thanks in Advance