Hello,
I usually work on e-commerce and I have used multiple payment gateways and I have complete idea of how it work and what configurations we need to do.
If you want to discuss details, feel free to initiate a chat. I would be happy to explain you the whole process.
Please check my profile review for your ready reference about my work and feedbacks:
https://www.freelancer.com/u/akash9958.html
Thanks Akash