Programmatically add a node

Question

Some years ago I made a Drupal 7 site. I want to remake the site with Drupal 9.

In Drupal 7 I added nodes programmatically with this PHP code.

define('DRUPAL_ROOT', getcwd());
require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

$data = $_GET['d'];

AddNewNode($data);

function AddNewNode($data) {
  list($installlanguage, $playerid) = explode('|', $data);
  $node = new stdClass();
  $node->type = 'new_install';
  node_object_prepare($node);
  $node->language = LANGUAGE_NONE;
  $node->field_hm_new_installlanguage[$node->language][0]['value'] =   $installlanguage;
  $node->field_hm_new_install_playerid[$node->language][0]['value'] = $playerid;
  node_save($node);
}

The code doesn't work in Drupal 9.

I tried to search Google for drupal 9 add content programmatically, but I don't seem to get any useful result. Most links are about Drupal 8.

I also tried the following code, but I get this error.

Fatal error: Uncaught Error: Class "Drupal\node\Entity\Node" not found

use \Drupal\node\Entity\Node;

$data = $_GET['d'];
AddNewGameInstall($data);

function AddNewGameInstall($data) {
  $node = Node::create([
    'type' => 'new_game_install',
    'language' => LANGUAGE_NONE,
    'field_device_language' => $devicelanguage,
    'field_player_id' => $playerid
  ]);
  $node->save();
}

Can someone point me in the right direction?