Fatal Error in /admin

[HERMES Space]

Hello, 
I have some troubles on my website.
I just installed Prestashop 1.7.8.8 and did all the installation steps but when trying to reach my /admin page, I first had a error 500 page, that I've fixed using a method found in another topic, where I had to edit some code in /config/defines.inc.php
So just like that, the error 500 was gone, yet there is another problem, as following: 

Compile Error: main(): Failed opening required '/home/hermesd/www/store/admin/../autoload.php' (include_path='/home/hermesd/www/store/vendor/pear/pear_exception:/home/hermesd/www/store/vendor/pear/console_getopt:/home/hermesd/www/store/vendor/pear/pear-core-minimal/src:/home/hermesd/www/store/vendor/pear/archive_tar:.:/usr/local/php7.4/lib/php')

in index.php line 81

So I went to the line 81 of /admin/index.php, and here is what the line says:
 

try {
    require_once __DIR__.'/../autoload.php'; 	//This is line 81
    $response = $kernel->handle($request, HttpKernelInterface::MASTER_REQUEST, false);
    $response->send();
    $kernel->terminate($request, $response);
} catch (NotFoundHttpException $exception) {
    define('ADMIN_LEGACY_CONTEXT', true);
    // correct Apache charset (except if it's too late)
    if (!headers_sent()) {
        header('Content-Type: text/html; charset=utf-8');
}

So if I'm not wrong, there should be a file called autoload.php in the root of my shop, yet there isn't, so should I copy and paste it from somewhere else?
I've taken the autoload.php from /prestashop to test that and pasted it into my root and it looks like it's working, but I'm pretty sure this is not the right way to do it, so please help me out. Thank you!