How I can add new page in to menu (with sub menu with sub pages)?
To add new_page with sub pages sub menu, you should open header.php and add these lines (where 999 is ID of that new_page)
<?php $new_page_ID = 999;
><?php echo get_the_title($new_page_ID);?>
-end of new_page submenu->
-end of new_page->