I’d make the nav 100% width. Also a popular thing right now are divisions in content. So for that welcome area, have that be one module rather then running the full length of the page. you could even run it 100% width and have the sidebar over it or grid style layout. Add some more imagery for more intrest.. Social media icons even for color.
As for visual hierarchy, the content area (considering a change?) under the nav but before the main area is really low. It’s close to the top but blends into the background. If you want it a 1-2-3, lighten the area, make the text/header large, or re color it.