long loading time

Hi,

Modules can't have pagination.

I understand that you have created one products listing module per sub category, and then, in a Joomla article, you insert the different modules one after the other so that the products can be separated per sub category on the Joomla article page, each time with the sub category name before the listing of its products below.
A solution would be to split the Joomla article in several articles, and instead of having one page with one article, you could have a page of a listing of articles, each time with a module in it. Then, you could use this extension extensions.joomla.org/extension/ajax-infinity/ so that the Joomla articles would be loaded on the fly when you scroll down, instead of having to load everything during the page load.

However, did you know that a normal HikaShop products listing page can do that too ?
If you create a menu item of the type HikaShop products listing for a main category (like Dibond), and set its "sub elements filter" setting to "grouped by category", it will group the products of the sub categories per sub category, similarly to what you've manually constructed. And what's great is that this display mode supports pagination, so you don't have to load all the products on the same page. That way, you'll be able to have a fast loading time.
I think that's the solution you want to use. The setup and maintainability will be way easier, it doesn't require a third party plugin, and it will load fast.