Why the post is so narrow?

Hi,

I use WordPress built-in theme Twenty Twenty-Four.

However, after publishing a post, I find:

1. The post is very narrow. Only about 1/3 of the total width. See this: https://pasteboard.co/BPj9nJXbdi3P.png . How to set post to show in full width?
2. The featured image appear above the title. How to hide the featured image?

The page I need help with: [log in to see the link]