Resizing a slider for phones

Hi,

I m trying to fit the format of my slider for phones and pads, but I m new and don’t know really what the best solution is. The slider is the one on the home page.

The website is dinettemagazine.com

the part of the css is this:

//@media screen and (max-width: 768px) {
.blog-wrap #primary {
-webkit-column-count: 1;
-moz-column-count: 1;
column-count: 1;
-webkit-column-gap: 0;
-moz-column-gap: 0;
column-gap: 0;
padding: 10px;
float: left;
}
.entry-thumbnail span {
visibility: visible;
position: initial;
display: inline-block;
width:50%;
text-align: left;
font-size: 1em;
margin-left: 15px;
vertical-align: top;
}
}//

what should I add to solve my problem.

Thank you