Hello!
Briefly about the essence of the task: the standard theme is set in opencart, it turns out that the categories (collections) of goods and the list of single goods are displayed on one page, you need to make a switch, i.e. clicked on the button shows only the collection of goods, clicked on another button - the goods appeared.
Problem: in order to differentiate the output of goods and collections, you need to find the controller file that outputs them, which I can’t cope with for three days, I read on the Internet that the catalog / controller / product / category file is responsible for the output of goods and collections .php - output product group, then I tried to edit it, but nothing happened, even if I erase all the code in that file, nothing changes, about 550 lines of code in php in it, i.e. Site behavior when category.php is empty and when there are 550 lines of code in it is no different, which is very strange to me. But, suddenly, if this file is deleted altogether and not just the text in it, then the goods and collections immediately disappear, and instead of them a message appears stating that the requested page was not found, as a joke. So this file and the code in it for some reason needed.
Help please, I don’t even know what to do.