Integrating paypal (start to finish) in existing ecommerce site

Url: " [login to view URL] " is an ecommerce website that we have made on core php without any framework and purely coded. We are looking for someone who can do the integration of PayPal api. We will need help with understanding which api needs to be used. What i have is the business account, user id and passwords,. You need to guide from start, even the API code have to be your responsibility. I have a budget of 20$ for this, which I expect any expert and experienced developer can do in few hours only. But yes, if there is someone who goes extra miles to help me and implementing without any issues left, i can afford for additional $10 as bonus. Top to that, my positive feedback. Looking for freelancers from Indian region only Note: My own developer will be there, so freelancer and my developer both can mutually close this project to satisfaction. I will create two milestones fully paid. First milestone will be released after 2 test transactions. Second milestone will be finished after 4days but less than 6 days, where i will perform more tests, as well as my partners may also perform more tests.