After hours and hours I found this:
I added this route:
        $router->add('/admin', array(
            'module' => 'backend',
            'controller' => 'index',
            'action' => 'index'
        ));
now if I go to site.com/admin backend module called but for every sub addresses (admin/*) frontend (default) module called!
then I add this routes too:
        $router->add('/admin/:controller/:action', array(
            'module' => 'backend',
            'controller' => 1,
            'action' => 2
        ));
         $router->add('/admin/:controller', array(
            'module' => 'backend',
            'controller' => 1,
            'action' => 'index'
        ));
now every address in admin works perfectly and use backend module. but now the frontend site won't work correctly! (All addresses except /admin/* goes to index contrller of Frontend) and if I add this routes too:
        $router->add('/index', array(
            'module' => 'frontend',
            'controller' => 'index',
            'action' => 'index'
        ));
        $router->add('/', array(
            'module' => 'frontend',
            'controller' => 'index',
            'action' => 'index'
        ));
        $router->add('/:controller', array(
            'module' => 'frontend',
            'controller' => 1,
            'action' => 'index'
        ));
        $router->add('/:controller/:action', array(
            'module' => 'frontend',
            'controller' => 1,
            'action' => 2
        ));
now backend module (admin and admin/*) do not work!! :)) (frontend module called)
I'm so confused, please help me!