Need help with language helper

Can you help me ?
I cannot switch my language into my view.

Here is my config.php

$autoload['helper'] = array('url', 'file', 'language');
$autoload['language'] = array('homepage');

My view is on php like that : <?= lang('carousel_title'); ?>

My controller : public function index($language = 'french')

And here is my routes :

// Routes française
$route['fr'] = 'Page/index';

// Route Anglaise
$route['en'] = 'Page/index/english';


My problem, is for every url, i'm in french. /en didn't work. How set the default language for an user in my controller ?