What is the correct/better way to implement the menu and background?

Question

css

Hello, I can not understand how better or more correct to do

here is the menu

and a background that goes beyond the side-altars of the container, highlighted in red in the photo.

It is necessary that there be a fixed menu on the left that scrolls down along with the scrolling of the page, and sections are located to the right of it. Moreover, in the first section (the one with the cow) at the top there should be a header with a phone number, mail, search form.

I have now done this in the header and I think that this is not correct, since then I simply cannot adequately add other sections and I will have to write everything in the header.
This is how I have it now https://codepen.io/pen/rNOJMpv

Answer 1

For example, yes. Hastily assembled.
code pen