Hello Alejandro,
To answers your 2 questions:
1. Because your home page is using contained content which removes the paddings. In order to be able to adjust the paddings, you’ll need to change the “content container” to Default in the layout metabox of the page.
2. Are you referring the Primary Navigation? If so, then Go to Customize > Layout > Primary Navigation > Navigation location > No navigation
Articles that will be helpful:
Where is layout metabox: https://docs.generatepress.com/article/layout-metabox-overview/#where-is-it
Content container overview: https://docs.generatepress.com/article/content-container/
Let me know if it works!