Cache problem on Cart

When I add items to the cart and click the cart symbol. Nothing appears in the sidebar. I can only enter to see what is in the cart if I enter through the specific URL of the cart, but nothing appears in the sidebar when pressing the cart. Just a blank space as if it were empty. I was investigating and it may be a cache problem, I have to exclude the cart, but I’m new to this. This page that I have was designed for me by a person in fivver. Would you help me to solve this problem?

The page I need help with: [log in to see the link]