Hi,
I suppose that you're talking about when you're browsing your website on a smartphone, because on my computer I don't see any problem.
That actually also comes from your Joomla template.
Go in the menu Display>Views of HikaShop and remove the view customization of the file "cart" of the view "checkout" and that will fix the problem.
But again, it would be better to contact your template provider for help. They should be able to provide a correct view override. Because if you remove the override, you'll loose the styling of the cart you template provider made.