If you’re trying to replicate an old site then i would suggest starting from scratch and not importing a site, as this will add functions, features and CSS that does not match your original design.
It would be easier to start with a blank page.
For your home page i would set the Content Container to Full Width:
Then build your page with the GenerateBlocks plugin, this will allow you to have full width backgrounds/containers where you need them. Just treat each section of the page as a separate Container Block.