Dynamic JS and CSS files causing slowness

hello, one of my clients is using the Nevada theme by United Themes and is experiencing extreme slowness. I narrowed the slowness down to four files, dynamic.js.php, like.js.php, custom.font.php, and style.php. The reason for the slowness is that each of these files is dynamically generated by the server on each page load which takes some time. since the site is not moving or being developed anymore, these files will be the same everytime and do not need to continuously be dynamically generated. I was wondering if there is any easy way to just load static copies of these files instead of the .php versions? thank you