Thanks a lot, again @Kyle_W !
your responses are very clear.
however, I’m using Storefront and Admin API with a react app
I want to use not Vivawallet - as I said by mistake in my first post - but PayGreen which is not a third payment partner to shopify. I also want to use a delivery service (coursier.fr) which is also not a shopify partner.
Here is my need:
Create a checkout with storefront api > use the paygreen api to do the payment (via an iframe) > then, when the payment is successful (paygreen send the response to my server), mark the transaction and checkout as paid. I want to make a payment with PayGreen but keep the benefit of the shopify product management system.
is it clear? Sorry my english is so bad 