Change Authorize.net payment gateway to Square in custom built membership sign up system in Opencart

I have a site in Opencart 2.2.0.0. I have two things to make payment in my site. 1. First thing is for multi-step affiliate user registration form where if a user tries to register as affiliate user he should first pay the amount and they will be registered. 2. Second thing is products in my website. Which is working very well. I was using [login to view URL] for both of the payments. for 2nd (product sales) I can create API keys and integrate Square by myself. Affiliate registration form is also working fine but I just need to change payment method from [login to view URL] to Square. A freelancer from freelancer.com created that affiliate registration form with payment with [login to view URL] before but he is not in contact so I need you to change payment method from [login to view URL] to Square. Please make sure you can do this job in my budget $50 Here I have attached two screenshots for your demonstration.