I Need Website Testing and Fixing

Hello, We had a freelancer site made for us that's targeting college students to get help from other college students with their homework. Last week, we started testing it live with other students and they encountered bugs and all sorts of issues with it. So we're looking for a programmer or a team who can test the site, fix up the code and make it run like it's supposed to. Although the site is already mostly mobile responsive, it still has many issues that need to be fixed. Some parts don't resize properly and stuff like that. You'll need to know how to integrate payment processors and troubleshoot them. Since it's a freelance-style site, you'll need to ensure that funds transfer properly from user to user and fees get charged according to the fees we specify. Paypal and [login to view URL] are the two processors we're using. Also, uploading documents when a project gets created should work whether you're on a PC or on a mobile device. That's the biggest issue that happened... students on their smartphones could not upload or attach their documents to be uploaded to the site. The site is written in PHP and it uses MySQL Database. We've also attached a word doc that specifies some issues on the overall look that we need updating. Review this carefully and bid taking the details on that document into consideration. Please remember, if we choose to work with you, we simply want a fully-functional, bug-free website. You must be willing to provide that for the price you bid. Regarding Payment... we'll gladly pay 25% upfront to get started. When the site is displaying properly on all mobile devices, then we'll pay the next 25%. Then finally, when the site has been tested and is running smoothly without any bugs or issues, then we'll pay the remaining 50%. These are our terms. Just look at our feedback and you'll know that we treat our programmers with respect and consideration. There will be an additional "Bonus" as a way of saying thank you if you do this right and do it within 30 days. How much would you charge to go through the code and fix up the issues? How long do you think it would take you? Sincerely, Jaime P.S. I prefer to work with USA based programmers.