Redirect after user pass form submit
I found a solution. I compared the output from a dump of user_pass $form and contact_message_personal_form $form variable. 
My problem was, that my $form['actions']['submit']['#submit'] array was empty. So I added the missing '::submitForm' parameter 
and everything works.

function module_form_alter(&amp;$form, $form_state, $form_id) {
  if($form['#form_id'] == 'user_pass') {
    $form['actions']['submit']['#submit'][] = '::submitForm';
    $form['actions']['submit']['#submit'][] = 'user_pass_redirect'; 
  }
}

function user_pass_redirect(&amp;$form, $form_state) {
  $url = \Drupal\Core\Url::fromRoute('entity.node.canonical', [
    'node' =&gt; '87',
  ]);
  $form_state-&gt;setRedirectUrl($url);
}


I have no idea why my variable was empty but this works for me.