Trying to change sidebar-width

Hello all,
Right now, I am using the business theme and using CSS_editor module to make changes to the CSS. When inspecting the page as seen here:

When I change the 33.333% to 25%, it looks how I would want it. I’ve tried applying the following:

#sidebar-first{width: 25%;}
.col-md-4 {width: 25%;}

but neither of these when applied change the value of the width. Am I not using the correct tag?
Thankyou in advance.

Drupal version: