It looks like you added code to your css which interupted the way the responsive code works in the theme by default. The code that is affecting everything is the width that you added around line 3897 –
.epik-purple .home-feature-bg-dark .featuredpage .page, .home-feature-bg-dark .featuredpost .post {
width: 1140px;
}
When you add that width, it causes that section to be 1140px (even on mobile devices). But I don’t think you would need to add that since the theme’s width is already set to 1140px and is designed to be responsive when a mobile device is being used.