WordPress Full width

Hello all,

I have example, and I want like him in my website, I think it’s simply for the amazing designer here.

See the image:
https://prnt.sc/gna65q

I want like this:
My blog post content in the center
Custom size like 790 px
Different colors on both sides

I am use Customizr theme, WordPress, and I am disable all layouts.

But the post page is full, So, you know I want like the example,

See my theme: https://prnt.sc/gndjmn

Problems:
– There is no custom size for the content
– There are no spaces on the sides in different colors.