How to integrate a payment solution for a marketplace in Django?

Question

The concept of my website is something like a fiverr marketplace - people can request something, other people can offer something to this specific request. The requester can choose what to buy from the offering person(s) and I will take some fees of it.

I really do not know where to start. The refunding option, the pay-out for content offering user.. obviously, I want to make it as easy as possible for all involving persons. Should I receive the money and the content offering user has a balance on my site? If yes, how about the pay-outs? Should I just split the payment, like fees to me, payment to the offering user?

Where should I start?