Drupal 8.x

I'm in week 9 of trying to get a Drupal 6 site upgraded to Drupal 8. After lots of frustration (I'm kind of thinking that even though the site is several hundred pages, it would be easier and faster to start entering data manually - and I know it would be easier to just build a site from scratch the the proper tools to manage the content that needs to be managed, but the client has a requirement to use Drupal), I have finally gotten it to a point where it appears that the drush migrate-upgrade script will run.

Hi I need to create a side block using the parent items of main menu.

In my file.theme i wrote

$menu_tree = \Drupal::menuTree();
$menu_name = 'main';
// Build the typical default set of menu tree parameters.
$parameters = $menu_tree->getCurrentRouteMenuTreeParameters($menu_name);

// Load the tree based on this set of parameters.
$tree = $menu_tree->load($menu_name, $parameters);

So in my page.html.twig i wrote

{{ dump(tree) }}

But the result is NULL.

What is my error ?

Noticing that the ckeditor_font module together with the font add-on from ckeditor.com works so well, I created a ckeditor_templates based on the ckeditor_font module, module and put the Content Templates add-on from ckeditor into d8site/library/ This works! I can see the templates when creating content. But when I remove or add new templates to the D8site/library/templates/templates/default.js, I do NOT see my changes.
What am I missing?

Search API 8.x-1.0-alpha13:

Created Server and Index on a single text field in custom content.

When I click the Index Now button, I get the following error:

Could not load the following items for indexing on index Test Search: "entity:node/1308:en".

What causes this error?

I'm looking to rebuild my site to D8 and one of the key features I've built up on the site is the forums. On the D7 version of the site, I'm using ACL and Forum Access. I used these so I could setup restricted forums and containers, which allowed for a staff area. A forum that only those with permission could see and post in.

The default Drupal 8 installation contains 'Home' in the main navigation. I want to add a new item (say News Letter) to this menu but do not want to link it to any url. Instead, under this I want to create three second level items, which will be linked to a url (content), as shown:

Home
News Letter
-- Main News letter
-- Special News letter
-- Annual New Letter