Changing opacity, and bg color of tg container, etc. but keep text opacity

Hello,

Would someone mind helping me figure out how to change the opacity and bg color of the header and tg-container, etc. without influencing the text color and opacity as well?

Please see picture reference for what I want it to look like versus the link provided on thread:

https://eratovin.com/wp-content/uploads/2017/10/Screen-Shot-2017-10-28-at-3.14.19-PM.png

Many Thanks,
Daniel

The page I need help with: [log in to see the link]