Gaerwn on "[Theme: Hannari] How to display left sidebar after page content on mobile"

I am using a child theme. I have tried with the following code in the style.css of the child, but is not working:

@media screen and (max-width:768px) {
.left_sidebar .sidebar {
   float:right;
}
.left_sidebar .pagecontent {
   float:left;
}
}

Any sugestion about what should I do to have the left sidebar displayed after page content on mobile?

Thank you