Module development and code questions

In drupal 9 we are trying to integrate a payment platform's API where users will be able to "register" for a conference using webform where the initial submission is stored. We'd like to then send that information from the webform (name, email, number, package with price) to their platform using the POST method and allow the system to use their redirect link.

I have added blocks to twig templates via the UI or Twig Tweak but I have a custom form module that I'm trying to insert a simple custom block that will be localized. Not finding any examples out there so my question is if it's possible withing say the buildform() function?

I see plenty of examples for adding form to a block but not block within form. Is it doable?

I am using Drupal 8.

I was trying to use the drupal export tool found in 'admin/config/development/configuration/single/export'

The way I understand that I have to "export" the content types and their fields is by selecting them in the selector and copying and pasting the structure in a file with the name that appears below

What I was trying to export was a content type with its fields.
I was able to export both, the fields and the type of content, I put this into a module that I created, inside "config/install".

How to disable the entire navigation ( left, above, below, etc ) for a  site or more sites within a webpage? 

E.g.  webpage = www. site.com and target site which should be visable without navigation = www. site.com/es/site 

Still using Drupal 7

Thanks a lot in advance :-)

I would like to populate link field from entity reference to another link field in my content edit.

Here is my module code : 

Please remove. I posted the question in another forum.