Resize Sidebar

Hi,

I attempted to resize the sidebar in the fashionistas theme by simply editing the style.css with the following:

.site-sidebar {
width: 200px;
}

Unfortunately after this edit if I re-size the browser the sidebar loses it’s responsive qualities. Try it here https://https://www.vandal4hire.com/

The sidebar no longer drops down under the content so it’s suitable for mobile layout; instead it moves to the bottom right corner of the screen. I’m pretty new to CSS so any help would be really appreciated!