Integrate payment gateway prestashop

Question

I am trying to integrate a payment gateway into my prestashop website. I have the companies API, but unfortunatley they do not yet have a plugin on prestashop. Can anyone please suggest where I should start from or how I can go about getting this done.

What I think: I’m assuming prestashop saves order information in a file I can access through my file manager. So maybe I can write some code maybe in xml that retrieves the details requested by the paga api from the prestashop file. I don’t know if I’m thinking correctly. Can you guide somehow?

Thanks in advance