Hello mr. Aizaz!

Thank you for your answer.

In the left side MENU (Categories) is working fine, but I was talking about the MAIN MENU NAVIGATION. When im trying to add it as an HTML Block, I save it and then it goes back to Default.

How I add the HTML Block in this menu as it shows in attached photo?

And the other thing I need is if I want to add more categories in this main menu, want to be aligned in the center the extra category.
Thank you.