Sidebars

Hello, so I wanted to center my content in the middle of the page just as shown in the website, the problem is I wan’t to expand the size of the width with couple of cm on the right and couple on the left, I have used the customizer but when I change the sidebar width it doesn’t affect the left side it expands only on the right side and when I increase the content width nothing changes thank you

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