Thanks for the details… now for the bad news…to achieve what you want to do is actually a hard job to do because the content area has an inline style that is attached to the theme customizer which lets you choose the background colour for that. However, this is global. You would have to target the page ID and override the background colours for the containers in the page you want black by doing this with a custom CSS (ie: child theme or a plugin that lets you edit CSS). You would also have to “force” the background colours so that the inline styles are ignored that are applied directly on the containers, such as the #content-wrapper
Forcing a style is done with an exclamation mark ! and the word important
eg: background-color: #000000!important;
Your page ID is found on the tag which is how you would target the page and not others when you do your custom CSS.