Drupal 8.x

I have a views tpl where I set a variable but nomatter what I do, I can't get the output as a string ... even-though the drupal dump is indicating the value is set before AND after the output.

{% set foo = 'bar' %}
{{ dd(foo) }}
{{ foo }}
{{ dd(foo) }}

Hello,

I have just installed the Simplenews subscription module on Drupal 8. I have activated the module but it shows "First Name" and "Last Name" along with "Email" field. I want to remove the fields, but unable to find them. After spending most 8 hours, I could not find. it. google was not help at all.

Please help.

I added a new content type naming 'Custom Page'. I want to create a new template for all of the content with the content type 'Custom Page'.

I added the below code into my custom.theme file:

function yan_theme_suggestions_page_alter(array &$suggestions, array $variables) {
  if ($node = \Drupal::routeMatch()->getParameter('node')) {
    $suggestions[] = 'page__' . $node->bundle();
}

I understand that it needs to create a file xxx.html.twig in theme/custom/templates, right?

After an update I get an 500er error:

[01-Sep-2021 15:42:20 Europe/Berlin] PHP Fatal error:  Uncaught Error: Class 'ComposerAutoloaderInitDrupal8' not found in /homepages/16/d123456789/htdocs/drupal8/vendor/autoload.php:7
Stack trace:
#0 /homepages/16/d123456789/htdocs/drupal8/autoload.php(16): require()
#1 /homepages/16/d123456789/htdocs/drupal8/update.php(14): require_once('/homepages/16/d...')
#2 {main}
  thrown in /homepages/16/d154844430/htdocs/drupal8/vendor/autoload.php on line 7

Does anybody know what the problem is?