Sidebar width and mobile responsive

Hello!

I add to Virtue free theme this CSS code:

@media (min-width: 980px) {
.main.col-lg-9 {width: 66.66666666666666%;}
aside.col-lg-3 {width: 33.33333333333333%;}
}

.container {
width: 970px;
}

It works fine but it is not mobile responsive. How to change the code that will be mobile responsive? I want right sidebar around 270 – 290 px and theme width around 970 – 980 px.

Thanks.

Best regards.