Hello
for changing header sub menu items hover color go to dashboard >> appearance >> customize >general configuration >> header settings >> find Header Sub Menu Hover Color color palet >> select the color you want >> click on publish to save the changes.

Elementor only allows you to edit the inner pages not the template of our theme.
if you want to see the code then go to dashboard >> appearance >> theme editor >> search for the template-parts folder and open it >> you will see all the section files there you may edit the code there and add the link to the section you want to

please send us a link or screenshot on [email protected] so we could see where exactly you want to change the background or you might send us a link of that page.
also please tell which color you would like there to be as a background.
Thank you