Shopify PayU API Fix

I got these links ([login to view URL]) and ([login to view URL]) which has all the API integration information, I have two Shopify stores right now (so its basically the same work I need for both), and my payment gateway on Shopify is PayU Latam, the problem I am having is when people are going to pay it redirects them to PayU but some people don't push the button to return to my website so some orders aren't registered. I contacted PayU and Shopify and they said I can implement the PayU API integrations to fix the problem and get them to pay on my website. My store links are: [login to view URL] and [login to view URL] Now I want to know if I can get a developer to do these API Integrations on Shopify?