Custom css on premium news woo theme not working

Hi, just wondering if ayone can help me out. Im trying to customize a good deal of .css code for the Premium News theme by woo. The support team recommends doing all edits on the custom css style sheet to avoid losing customizations if the theme is ever updated.
The problem is, im just getting started on the header area and almost none of my customizations are going live. I assume there is something in the style.css sheet that is overriding my custom code, but even with the important tag its not overriding that command.
any tips or advice would be helpful! Im teaching myself html and css right now and admittedly im only beginning to understand it all so im totally green here.

thanks!