Hi there,
to cover some basics:
Pages such as Category and Tag archives are not regular pages. So they cannot be directly edited, as they are the result of a dynamic query that gets displayed using a theme template.
In GeneratePress Premium you can rebuild that template using a Block Element.
1. in Appearance > Elements –> Add New —> Block Element.
2. set the Element Type to: Loop Template
https://docs.generatepress.com/article/block-element-loop-template/
3. set the Display Rules > Location to: All Archives
4. Now in the block editor add a Query Loop Block. In the Query Loop Blocks settings check the Inherit Query from Template
5. Publish that element.
Now when you view that category page it will use your block element loop template.
Edit the Loop template to how you want.