Sometimes, the default top menu of Magento 2 doesn't meet all of your requirements or simply does not match your website's theme. And you want to change it with another that's better and more suitable.
In this tutorial, we'll show you an easy way to replace Magento 2 default top menu by using Ninja Menus, a powerful Magento 2 mega menu builder: https://www.magezon.com/magento-2-mega-menu.html

1. Create a new menu
First of all you need to create a new menu. Ninja Menus gives you the ability to create on quickly using drag & drop interface.
You can follow this guide for detailed steps: https://blog.magezon.com/how-to-create-mega-menu-in-magento-2/

2. Change top menu
In the edit page of the menu, open General tab and find Identifier field. In this field, enter "top-menu" and the current top menu of your site will be replaced with this one. Super easy, isn't it?