top menu items

Can I change the top right menu items (what’s the official name for this menu?)
About, recent works, testimonials… Etc.
And can I link those to new pages? or just to a spot on the homepage using #

hey there

Yes, of course, you can do this from the Appearance > menus
This is the default WordPress function:
https://www.wpbeginner.com/beginners-guide/how-to-add-navigation-menu-in-wordpress-beginners-guide/