Move sidebar within "content" div

Hi, I trying to integrate the blog elements of wordpress into my current website. I am not interested in building my website with wordpress.
I’ve tried to follow tutorials on how to do this, but they’re a bit outdated – so I still have a white column showing, and the sidebar won’t stop scrolling.

I’ve provided images to explain what I mean:

What my set-up actually looks like across the website
https://i173.photobucket.com/albums/w57/beccygme/a23a94d5-23a0-4592-baff-f7f060232e12.png

After trying to integrate
https://i173.photobucket.com/albums/w57/beccygme/ec7d2d1d-5dbd-40b2-94c6-219d3575be8f.png

Ignore the massive “Hello World!”, I’m so focused on fixing the sidebar part first, before moving on.

But as you can see, the sidebar content has jumped down the page, so it isn’t actually showing in the screenshot. But it does scroll with me once I get past a certain part.

In summary, I want that white section gone, yet still have the sidebar content next to my posts in the main content area. If I can get it to stop scrolling with me, as well, that would be great. But moving the sidebar and removing the white column is the main priority.