Responsive Sidebar Width

I have problem with the width for both primary and secondary sidebar for 240×320 size. I need to set my sidebar width to be the same as the main content width.

This is my site: https://bestlifequotesblog.com/

This is my CSS code:

#main {
padding: 10px;
}
.main-wrap {
float: left;
margin-left: 1rem;
margin-right: 21rem;
}
#sidebar-primary-wrap {
float: left;
margin-left: 1rem;
margin-right: -21rem;
width: 20rem;
}

#sidebar-secondary-wrap {
float: left;
margin-right: -20rem;
position: relative;
width: 20rem;
}

How to write the media query for this?