Woocommerce different language on backend

I have made two languages for backend and frontend. For frontend is default var “WPLANG” and for backend will be “admin_WPLANG”.

I have made options in woocommerce general settings tab. There is two language options for backend and fronted. When I select and save the option its not changing the language, I must to reload page again … What do I need that on option save it could change the language in backend?

My code:

add_action( 'woocommerce_update_options_general', 'update_settings_tabas', 10);
function update_settings_tabas(){
    update_option('admin_WPLANG',$_POST['admin_WPLANG']);
}

add_filter( 'locale', 'change_language_backend', 99);

function change_language_backend( $locale ) {
   $language = get_option('admin_WPLANG');
   if(is_admin()){
       return $language;
   }else{
       return $locale;
   }
}

https://wordpress.org/plugins/woocommerce/