Hi,
I have an issue when adding products to the cart. If I add a product, it does not appear on the cart.
and If you try, please try adding one product at a time to the cart.
I have found that you are using the older version of the theme, please update the theme to 7.0.1 version and update all the plugins as well, I am sure your issue will be solved.
There is an issue with the 3rd party plugins. Please deactivate all the 3rd party plugins and activate only theme-required plugins on the site and then check the issue. I am sure your issue will be solved.
Otherwise, keep the 3rd party plugin deactivated and send me the WP admin login details so I will check and solve the header issue.