Drupal 8.x

Sorry for a newbie question.  I installed Language Switcher Extended.  Everything works properly, but I need to align the Language Switcher block right in the Header region.  My theme is Drupal8 W3CSS Theme.

Now I have the following html source of my Language Switcher block

I want to add a webform on a certain basic page content type but not on other pages. How could I do that? Could anyone please let me know the steps involved in doing so. I am using Drupal 8.7.9

The site page in question is as follows.https://japaneseautoworld.com/virtual-hybrid-battery

I've created a custom field type and can save a setting in the field type (a simple select list populated with taxonomy vocab)

With the field type I've created a widget and need to be able to see the vocab selection from the main field type so I can populate a select populated with the terms for the desired vocab.

How can I get to the settings of the field type from within the widget code?

Installed Drupal8 on the LAMP web server of the Ubuntu 18.04.3 LTS operating system.
But when in the toolbar I click on the Content, Structure, Appearance tabs and all the others, I have an error:

404 Not Found

The requested URL was not found on this server.
Apache/2.4.29 (Ubuntu) Server at localhost Port 80

How to fix the error?

My goal is to create this site where an organization (or the representative of the organization) can register to as a "main user". Then they can add users under that organization that can also log in to the site. So you can't register yourself as a regular user, only as a organization. Basically it would look like this:

USERS:
    - Organization X (main user)
        - John Doe (user)
        - Jimmy Johnson (user)
        - Andy Andersson (user)
    - Organization Y (main user)
        - Frank Frink
        - Jane Doe

I followed this guide to convert my project to a composer project. When I try to access the site or when I go to /update.php I get this error: