Hi,
If you want to integrate with a new payment gateway, the best is to create your own payment plugin.
On our developer documentation, we have an example payment plugin you can rely on to build your own payment plugin:
www.hikashop.com/support/documentation/6...r-documentation.html
The files of this plugin are heavily commented so that you can understand what needs to be done.
You can see there that the "payment checkout variables" are available in the onAfterOrderConfirm function in the $order variable.