Why the changes in style.css are not reflecting in my webpage

I am using Sydney theme . But I want to change the padding of my container class of pages. But my changes are not reflecting in my website . It works fine in DevTool when I am changing the padding there but not in the css file.

.page .page-wrap .content-wrapper,
.single .page-wrap .content-wrapper {
padding: 30px; // I want to change 30px to 0
}