Making a single border around two sections

Site URL: https://pear-hyperboloid-dn2z.squarespace.com/

Password :: ProfileSite22

I am looking to create a look similar to this page :: https://www.apple.com/airpods/
The way that there is 1 background colour going down the site, with each section having a rounded image block separating. If you look on the Squarespace site there is the landing section, a thin grey blank section, a gallery, and a services section. I want this background of that grey following that width of the think blank, wrapped around the top of the gallery, around the edges and underneath the services section with the accordion.

The colour I want this border to be is #E7E7E7. And the gallery block to have a rounded edge.