I need to change some settings in the "category list" and in the "item page".
I would like to edit the code to relocate the categories, titles and so on.
What are the pages in which to make the change?

This would be done in a k2 template or k2override
getk2.org/documentation/tutorials/item/174-templating-with-k2-and-the-concepts-of-sub-templates
make your changes to item.php, category.php, and category_item.php