I got to display the same menu as the header menu on sidebar and I created another root category in admin. Now I want to display the new root category in the main menu(header menu).I am new to Magento and PHP programming. I would really appreciate it if someone tells me what to do step by step. I know I need to override some php classes for Mageno_Theme module which creates the header menu but I do not know how to do that.
As you know in Magento 2.1 in admin you can only set one root category (Stores -> All Stores -> Main Website Store -> Root Category) which made me to only choose one root category and now ? I do not know how to use the other one for my main menu.