Menu problem

Hello! I’m trying to add language option to my website. I’ve coded my theme and I need to show the web in three different languages. I’ve got the little flags and I’ve managed to pass a php variable with the language it’s selected. With that variable I’ve made a if for the wp_nav_menu assignment in the header.php. It works actually. When I change the language the correct menu in the correct language comes up. The problem is that when I hit in a menu item and the selected page opens the menu is gone. Disappears. Can anybody help me, plase? Here is the code I use.

In header.php

if ($language == 'es') {

wp_nav_menu(array(
		'theme_location' => 'spanish',
		'container_class' => 'main-nav',
		'container' => 'nav'
));

} else if ($language == 'en') {

wp_nav_menu(array(
		'theme_location' => 'english',
		'container_class' => 'main-nav',
		'container' => 'nav'
));
} else if ($language == 'de') {

wp_nav_menu(array(
	        'theme_location' => 'german',
		'container_class' => 'main-nav',
		'container' => 'nav'
));
}

And in the functions.php

add_theme_support ('menus');
//Create Nav Menu
if (function_exists ('register_nav_menus')) {
	register_nav_menus (array(
                               'spanish' => __('Spanish menu'),
			       'english' => __('English menu'),
			       'german' => __('German menu')
        ));
}