Only want to change header.php category name from ‘portfolio’ to ‘examples’

Basically, I want to know how to change the names in the menu.

I installed themeforest – ‘personal landing page’, but have been confused by other themes before.

My site: https://sevenstarconsulting.com

I want the menu across the top of the main section of my site to say ‘About’; ‘Examples’; ‘Services’; ‘Contact’

This is how it is in the rest of the site, just not the main header.
I try to edit header.php and only get a text file (using TextEdit on Mac) with a hyperlinked bullet list of my menu. Can’t edit this.

I set the file to 777 via Filezilla, edit it, and get error from my host. Can’t use theme editor…