Hello, Dimitris,
As we can see, the speed on the dashboard is not particularly fast, and our theme does not affect it.
Additionally, we tested your website with the default WooCommerce StoreFront theme and experienced the same speed as with our XStore theme. This indicates that the speed of your website is independent of the theme activated on it, so theme support cannot assist you.
Given that you have the WP Rocket plugin activated, we would recommend that you contact their premium support for help, as they specialize in speed optimization.
Kind Regards,
8theme team