Hi there,
Option 1
In Customizer > Layout > Container set the Width to a very big number. eg. 10000px
This will apply to the entire site and all pages will span the width of the screen. But it will keep the themes padding.
Option 2 set the Content Container of a page to full width.
This can be done on a per page basis in the post editor:
https://docs.generatepress.com/article/content-container/
Or using a Layout Element where you can specify display rules for its application:
https://docs.generatepress.com/article/layout-element-overview/
This however will remove the Themes padding, so you need to add in a GB Container Block with padding for your content to site inside.
The latter option is generally the preferred method.