Hi,
Using the network developer tool of your browser, you can see what's the problem:
take.ms/PcmLyi
The homepage tab takes 7 seconds to be fully loaded.
But the page only takes 1.6 seconds to be generated by Joomla.
So the problem is not that Joomla or HikaShop are slow.
It's just that you have too many files that the browser has to download in order to display a page.
Between the CSS, the JS and the images, there are more than a 100 different files to download in order to display the homepage.
To avoid that, you can use an extension like this one:
extensions.joomla.org/extension/jch-optimize
I've checked a product page, and it took 35 seconds to load. So there is a problem with the generation of the page which takes almost all that time. As I explained in my previous post, you need to turn on the "debug mode" setting of the Joomla configuration and then check the profiling data at the bottom of the page in order to understand where is the issue.