<?php
# Create user
$lang = \Drupal::languageManager()->getCurrentLanguage()->getId();
$user = \Drupal\user\Entity\User::create();

$user->setUsername('username');
$user->setEmail('email@test.com');
$password = hash('sha512',uniqid(rand(), true));
$user->setPassword($password);
$user->addRole('role_machine_name');
$user->enforceIsNew();
$user->activate();
$result = $user->save();

# Edit user
$user_load = user_load_by_name($old_email);
$user = \Drupal\user\Entity\User::load($user_load->id());
$user->setUsername($new_email);
$user->setEmail($new_email);
$user->save();

# Delete user
$user_load = user_load_by_name($email);
$user = \Drupal\user\Entity\User::load($user_load->id());
$user->delete();
?>