fix errors in my site and add functionality with code already written

I have PHP website in which most of the code already created and the design files already created for every page in the project. I need them together. there might be some errors in functionality in the sign-up process, a mini cart plugin i need to have functional, and making sure the uploadable content is working correctly. I also have another feature I need to add in that was also already coded working inside the manage account overlay area. I have a list of some of the issues i found and need to be fixed. So I need a php expert to come in and complete the work. There will be 2 of you working on the project at the same time validating each others code to make sure everything is done correctly.