Instyle theme can't decrease padding

I can’t seem to figure out how to decrease the padding between the header and the body, and the body and the footer. What I want to do is have the header, body, and footer all on the same page so that any site visitor doesn’t have to scroll down at all to view the entire page. I have tried both adding in custom CSS to the Instyle theme options as well as changing the values of padding and margins in the style.css. I might not be changing the right values, but I have gone through style.css line by line trying to find the correct values to change. Is there something I am missing, or an easier way to do this?

The website is: https://www.r1environmental.com

Thank you in advance!