Hi there,
when building out pages with full width content, we advise you set the Page Builder Container to Full Width:
https://docs.generatepress.com/article/content-container/
This removes the themes padding and spacing – which is one of the reasons for the space below.
Then make sure all your content is added inside a GB Container Block to keep content contained whilst allowing for full width backgrounds.
For that last block i would build it using the FB Container, Headline and Buttons blocks. This will remove the bottom margin from the last block which is the another element creating the gap.