This looks like a copy paste bug to me:
$ppd_user['NAME.GIVEN'] = $user['billingaddress']['firstname'] != '' ? $user['billingaddress']['firstname'] : $user['billingaddress']['firstname'];
See
https://github.com/heidelpay-sp/ShopwareStandardModul/blob/master/Frontend/HeidelGateway/Bootstrap.php#L3014
This looks like a copy paste bug to me:
$ppd_user['NAME.GIVEN'] = $user['billingaddress']['firstname'] != '' ? $user['billingaddress']['firstname'] : $user['billingaddress']['firstname'];See
https://github.com/heidelpay-sp/ShopwareStandardModul/blob/master/Frontend/HeidelGateway/Bootstrap.php#L3014