class Chat extends Model {
    protected $casts = ['state' => State::class];
    ...
}
abstract class State {
    abstract public function handleTelegramUpdate($update, Chat $chat);
}
class DefaultState extends State {
    public function handleTelegramUpdate($update, Chat $chat)
    {
        if(/*the $update means a menu item is selected*/) {
            $chat->state = new SubMenuState(/*the selected menu item*/);
            //send the sub-menu to the chat.
        }
    }
}
class SubMenuState extends State {
    ...
}

    $update = getTelegramUpdate();
    if ($update is a chat) {
        $chat = $chatRepository->findOrCreate($update->chat_id);
       ...
       if($chat->state === null) {
           (new DefaultState)->handleTelegramUpdate($update, $chat);
       } else {
          $chat->state->handleTelegramUpdate($update, $chat);
       }
       $chat->save();
    }