FOX - Currency Switcher Professional for WooCommerce

Plugin URL: https://wordpress.org/plugins/woocommerce-quick-donation/

//in file plugins\woocommerce-quick-donation\includes\class-quick-donation-process.php add next code
if (class_exists('WOOCS')) {
    global $WOOCS;
    if ($WOOCS->current_currency != $WOOCS->default_currency) {
        $currencies = $WOOCS->get_currencies();
        $donateprice = $donateprice / $currencies[$WOOCS->current_currency]['rate'];
    }
}