Yes, you can able to change both by adding additional CSS in the CSS file.
for background bar menu color you can add this CSS in the CSS file.
Yes if you put your code above the announcement bar code then yore view like
And if you want the look like
then give announcement bar extra class and give css to it and set its possition using css.
sorry for the late reply, There must be you had added any additional CSS regarding header background so it gets conflicted (site-header) class will you can see all over the site so basically, it's common .for any additional customization you need professional help. And if you want to learn CSS (https://www.w3schools.com/css/)it will grate resource.
Did you use the same theme without customization? Please provide your site link for a better look.