Hello,
The infinite scroll is only available for product listing menus.
The current listing you have is a bit specific and I don't think that the infinite scroll is compatible with it.
Grouping the products by category would not provide a good result because if the loading stop in a middle of a category, the next loading will re-display the category title (because it can't know easily what was the previous loaded data)
So if you want to have a dynamic ajax loading for your page, it would be possible but it would require some customization in order to load the categories without the products and create a script to load dynamically the categories' content when the customer look at the corresponding page zone.
But I'm afraid that's not something really simple to implement.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.