Is there a way
So that if the user opens the multilingual website
The site is displayed according to the user's language

thank you

@7ala
Most probably not, as standard locales are different to ones used by osclass and it may be hard to do some kind of mapping.

I found an addon that does that, but unfortunately
The site is getting a little slow
Addition name auto_language
This code is from inside the addon

<?php
/*
Plugin Name: Auto Language
Description: Choose an automatic language base on browser language
Version: 1.0
Author: Guillermo Parraguez
Short Name: aLanguage
Plugin update URI: auto-language
*/

function check_language () {
$browser = str_replace("-","_",substr($_SERVER['HTTP_ACCEPT_LANGUAGE'], 0, 5)); //language in the browser
$list  = osc_get_locales(); //list of languages in osclass
$current  = osc_current_user_locale(); //current language in osclass


if(!isset($_COOKIE['osc_auto_language']) && !isset($_GET['auto'])){
setcookie("osc_auto_language", true, time()+60*60*24*90, "/");
if($current != $browser){
foreach ($list as $lan_code) {
if($browser == $lan_code['pk_c_code']){
header("Location: index.php?page=language&auto=true&locale=".$browser);
}
}
}
}
}
osc_add_hook('init', check_language());

?>
Is there an error
Because it works some of the time
And other times it doesn't work

@7ala
Does not looks to be issue there.
Maybe try to add after line:
header("Location: index.php?page=language&auto=true&locale=".$browser);
Exit command
exit;

I did the experiment
But the site speed is less than
70 to 48
cause slow
Is there a solution?

@7ala
Piece of code you put there does not seem to have any relation to speed of your site

Auto language plugin is needed for osclass, I think. Osclasspoint ? Hmm? 

Auto language plugin is needed for osclass, I think. Osclasspoint ? Hmm?