Full width SharePoint site for web parts

I'm having a hard time to make one of my SharePoint sites into full width with web content. I have done some research and found one possible soloution, which is to manipulate the manifest.json file, more info here; https://docs.microsoft.com/en-us/sharepoint/dev/spfx/web-parts/basics/use-web-parts-full-width-column.

Need someone to help me with this.

It's a SharePoint Online (Microsoft 365) site.

Fixed price.

Addition work in the future if you are the correct resource.