Try to add the following PHP code snippet to the child theme functions.php file to do this
function basel_get_owl_items_numbers( $slides_per_view, $post_type = false, $custom_sizes = false ) {
$items = array();
$items['desktop'] = ( $slides_per_view > 0 ) ? $slides_per_view : 1;
$items['desktop_small'] = ( $items['desktop'] > 1 ) ? $items['desktop'] - 1 : 1;
if ( $items['desktop'] == 6 ) $items['desktop_small'] = 4;
$items['tablet'] = ( $items['desktop_small'] > 1 ) ? $items['desktop_small'] : 1;
$items['mobile'] = 1;
if ( $post_type == 'product' ) {
$items['mobile'] = basel_get_opt( 'products_columns_mobile' );
}
if ( $custom_sizes ) {
return $custom_sizes;
}
return $items;
}