Looks like it can be fairly trivially achieved with a hierarchical custom post type and a menu widget in the sidebar. Menus come with current page CSS classes out of the box that can be styled as you require.
There is no option to click the button in header only on some pages
Are you using https://catchthemes.com/demo/clean-portfolio/ theme? I just tried following CSS and it changed the color on demo site .menu-toggle { color: #345789 !important; }
Images and menu links disapearing after saving
Drop down menu that updates block content
Add URL parameter to nav links based on domain
Header not showing in new pages
How do I highlight a WordPress Menu Item for a page that is not on the Menu?
wp_nav_menu_items callback not triggered
You have a second link (<a> tag) above the Home link in your menu. It’s linking to careers. Maybe you will look in your menu settings.