Drupal 8.x

In a content type I have various fields and among these I have 2 select list fields (the first text list and the second entity reference).
When I make the choice in the first select I would like the second to be updated with only the nodes connected to the first
I have done various tests and read various articles (some have caused me confusion because they talk about writing all the code in form alter without using the callBack), but it is not clear to me how to do it
In the first select I inserted the callback and wrote this code

I have created a Webform using Drupal 8.9.13 and Webform version 6.0.2 and I have existing textfield elements and hidden elements and I am using computed twig to calculate their values. This is working as expected but I now need to display these text fields into a dropdown options box. 

The export of the webform is:

Hello everyone,

I installed my Drupal 8 using composer.

I also use Wamp Server.

To display my home page, I must go on http://localhost/myProject/web/
Is there a way to display my home page without web in the URL, so http://localhost/Drupal8.xTestDev/ ?

Hi. Trying this again as I'm not seeing my previous post on this topic. 

I'm new to Drupal. Confused by the map related modules. What I'd like to achieve is to have a map that displays data from an external WMS (web map service) or GeoJson feed or similar. At my organization, we have lots of map services already published, often with lot's of data, so it's much more efficient to consume those, rather than re-creating that content in Drupal so that it can be displayed on a map. 

We are on 8x and moving to 9 soon.