The theme demo was created with the options to showcase them, although not a lot was done.
1. The header has a logo uploaded (Customize > Site Identity) and the navigation set to float right (Customize > Layout > Primary Navigation).
2. The feature section there is using the Page Header add-on. If you’re viewing the blog, you’d create it in “Customize > Blog”. If you’re using a static page (which it looks like you are), you would create it using the Page Header metabox while editing that page: https://generatepress.com/knowledgebase/generate-page-header/
Let me know if you need more info 🙂