Trying to adjust sidbar width

I can’t seem to find how to adjust the sidebar width for my theme. I am trying to make the sidebars width smaller and the middle section width larger. The web site is http://spyonberlin.com/ . I have found this in the css

global $sidebar;
if( $sidebar == “left-sidebar” ){

global $left_sidebar;
echo “<div class=’four columns mb0 gdl-left-sidebar’>”;
echo “<div class=’gdl-sidebar-wrapper gdl-border-y right’>”;
echo “<div class=’sidebar-wrapper’>”;
dynamic_sidebar( $left_sidebar );
echo “</div>”;
echo “</div>”;
echo “</div>”;

}else if( $sidebar == “both-sidebar” ){

global $left_sidebar;
echo “<div class=’four columns mb0 gdl-left-sidebar’>”;
echo “<div class=’gdl-sidebar-wrapper gdl-border-y right’>”;
echo “<div class=’sidebar-wrapper’>”;
dynamic_sidebar( $left_sidebar );
echo “</div>”;
echo “</div>”;
echo “</div>”;