Help with CSS styling for mobile compatability

Hey,

I’m trying to adjust the style of my site to make for a better mobile and tablet viewing experience using CSS. As a relative beginner to CSS – who has tried his best to figure this out on his own – I was hoping someone could help me figure out how to do the following:

-Eliminate certain features that are present on the desktop version from mobile or tablet versions, and, conversely, include others not present on the desktop version.
-Adjust the size and location of text and images based upon screen size.

I am currently using the Tesseract theme, which is a responsive theme, and I am also using Site Origin’s Page Builder.

Thanks for your time and I look forward to your response(s)!