Is it possible getting an object inside an object from a container without passing it as a reference with Symfony DI?

I'm trying to understand Dependency injections, and currently working with Symphony DI container.

I managed to get my container working in a very basic way:

Objects are created only when called. for example, if I remove the Database $database TypeHint from my SystemUser.php class, the database will not load.

How do I handle situations where I want to load a "Customer" class (see App.php) and that customer class needs the database object?

I do not want to create a new object of Customer, just get a reference of it from the container (if created) + have the Database class passed to it. but again, from the container.

Normally I would think that there are some classes which do not need any special objects like Database because they aren't using the database.

So how do I handle a situation where there is a special case where I need to create (or better say, fetch from the container) an object that does use the Database class, and it's far from being passed in a __construct.

This is the exmaple files I am working with:

index.php

require_once 'vendor/autoload.php';

use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Reference;
use TestingDI\Database;
use TestingDI\SystemUser;
use TestingDI\Customer;
use TestingDI\App;

$container = new ContainerBuilder();

$container->autowire( Database::class );
$container->autowire( SystemUser::class );
$container->autowire( Customer::class );
$container->autowire( App::class )
          ->setPublic( true );

$container->compile();

$app = $container->get( App::class );

App.php:

namespace TestingDI;

use TestingDI\SystemUser; 


class App {

    public $systemUser; 
    public $customer; 

    public function __construct(SystemUser $systemUser)
    {
        dump($this);
        $this->systemUser   = $systemUser;
        $customer = new \TestingDI\Customer();
    }

    public function __destruct()
    {
        dump($this);
    }
}

SystemUser.php

namespace TestingDI;

use TestingDI\Database;

class SystemUser {

    public $db; 
    public $id;

    public function __construct( Database $database )
    {
        dump($this);
        $this->db = $database;

        $this->db->changeTest(1);
    }


}

Customer.php

namespace TestingDI;

class Customer 
{

    public $db;

    public function __construct( Database $database )
    {
        $this->db = $database;
        dump($this);
        $this->db->changeTest(10);

    }
}

Database.php

namespace TestingDI;


class Database {

    public $pdo = "DATABASE: I'm a pdo instance <br>"; 
    public $test; 

    public function __construct()
    {
        dump($this);
    }

    public function hello()
    {
        echo "DATABASE: hello database <br>";
    }

    public function changeTest($msg)
    {
        $this->test = $msg;
    }
}