Integration of webmoney into crowdfunding Wordpress template, where to dig?

Question

Crowdfunding

Hello! The people who faced the more complex integration of webmoney into the topic? This means not just inserting a fundraising button as a donation, and not accepting payments for an online store, including plugins. There is a slightly different situation here, you need to "enter" a system of transactions into the pages of the template between the wallets of the creators of the fundraising company, the site administration and sponsors, deduction of interest after the completion of the program, and the return of funds to investors' accounts in case of unsuccessful completion of the company. In general, the question is for people who were involved in connecting webmoney, there are a lot of all sorts of sites they have, xml interfaces, I can’t master it myself) can we think together? ))
The theme itself is flexible for integrating payment systems, inside all the files are conveniently systematized, the problem is that I’m not strong in PHP, html, but with payment gateways it’s like in a fog in the forest, I don’t see where to put it point-blank, can you tell me )
Thank you all!
https://skywarriorthemes.com/fundingpress/2902-2/ - theme example
https://yadi.sk/d/9ZgjYSvc3RAg2S - theme archive