Sorry, this is T3 template from Joomlart.
Now is used JS and CSS optimalization inside template and now is not more what can owner do it for optimalization - only add support for webp and optimalization sizes of images.
With only click and setup from admin - this is end of optimalization.
Using cache or other plugins for optimalization is wrong way.
If you need load website quickly - 1-3 sec, then must comming develloper and change T3 and eshop completelly. (cca 50-150 hours, for develop, testing and more).
Look at the
www.zelenazeme.cz and look test in pagespeed insight from google.