Manual Testing of the Interface

I need a freelancer to manually test the interface of my web application. The expected outcome is increased user engagement, so it is important that the freelancer is able to identify any issues that may hinder this goal. As I do not have any specific testing requirements or test cases, I need the freelancer to create them. It is important that the freelancer has experience with manual testing and is able to identify any issues related to functionality and user experience. The interface being tested is a web application. Cost is Per screen basis