in category.php add line:

<div class="row element"><div class="twelve columns"><?php echo category_description(); ?></div></div>

BELOW

<div class="row">
            <div class="twelve columns  cat-title">
                <?php
                    if( have_posts () ){
                        ?><h2 ><span><?php _e( 'Category archives: ' , 'cosmotheme' ); echo get_cat_name( get_query_var('cat') ); ?></span></h2><?php
                    }else{
                        ?><h2 ><span><?php _e( 'Sorry, no posts found' , 'cosmotheme' ); ?></span></h2><?php
                    }
                ?>
            </div>
        </div>