Modify transparency of content area – Hueman child theme

I’m working on a child theme of the Hueman theme (terrific theme and documentation!)

I’ve become perplexed trying to make specific customizations to the CSS, and would welcome help!

I would like to:

(1)–control the color and transparency of the main text area (remove the white entirely). (I’ve found that the gray sidebars are image files which are easily disabled or modified.)

(2)-remove the side and content topbars which say ‘home’ and ‘follow’.

(3)–make the entire header area sticky (logo area and navigation bar), if this is possible.

I’ve searched the forum and haven’t found posts re. these specific questions.

site: https://www.aileen-conley.com

Thank you in advance.