Can I edit the product category columns? Don't limit them to just 2 or 4 columns?
What you ask for requires file customization which in reference to Item Support Policy is not allowed. http://themeforest.net/page/item_support_policy
So if you want to modify files and don't know how, you should contact your web developer. Item Policy says:
Item support does not include services to modify or extend the item beyond the original features, style, and functionality described on the item page. For customization services that will help you tailor the item to your specific requirements, we recommend contacting the author to see if they privately offer paid customization services or checking out the great service providers on Envato Studio.