Reply To: Problem with PHP

We are talking about the server response time. With a default theme it takes up to 4 seconds to load an almost empty cart page. Check the screenshot https://gyazo.com/fe922ba06d149ae7bf609fbfe1f86df1
It should be loaded in less than 1 second. While it is not loaded in that time, you will not get a fast website with any theme.
So you need to consult with your hosting provider for help on this matter.