Hi there,
First, you can set it so your featured image is below the title here: https://docs.generatepress.com/article/adjusting-the-featured-images/
Then, we can move the post meta below the featured image like this:
add_action( 'after_setup_theme', function() {
remove_action( 'generate_after_entry_title', 'generate_post_meta' );
add_action( 'generate_after_entry_header', 'generate_post_meta', 15 );
} );
Adding PHP: https://docs.generatepress.com/article/adding-php/
Let me know if you need more info π