Drupal 8.x

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: 

I have and existing site in Drupal 7 which uses Picture module for its responsive behaviour. Now I need to implement webp image extension for images, can not find any module or document for implementation of webp in Drupal 7.

Any Idea for the implementation?

With D7 support coming to an end I will need to change my 2 websites.

I've been runnig drupal since 2006, doing the work myself at an elementary level, developing in a hosted environment, using ftp.

This was work that may have taken more time then a pro would need, but it was doable.

Now I am trying my hand at D8+ commerce, which needs (?) composer.

It seems like every step I manage to take throws me another curve ball.

I did manage to install composer and a local development environment, and even had it running (I use ubuntu 19.10).