Module development and code questions

Hi,

I am trying to add a link to my Main Navigation menu. The link to my custom page looks like /text/{textid}/download. How can I add such a link to the menu?

Thanks,

Is it possible to create a media type programmatically?
I would like to use the already existing MediaSource "image" and do not use a new MediaSource.
Basically like the UI (/admin/structure/media/add), but programmatically?

Or does anyone know a plugin for Drupal Console that can be used to create Media Bundles/Types/Entities?

I'm using JavaScript from DataTables.net to provide some fancy styling on longer tables full of search results from a module I'm working on. My table definition is as follows:

I'm writing my first Drupal 8 module and on top of that my OO-fu is very weak. I've created a skeleton module and it works fine. Where I'm running in to problems is trying to make an admin page for settings. I'm using this as my guide: https://befused.com/drupal/drupal8-admin-form-guide. When I clear the cache, I get the following error in the logs "Error: Unsupported operand types in /var/www/html/drupal_2020/core/lib/Drupal/Core/Routing/RouteBuilder.php on line 163".

Hi, I'm using webform module in my drupal site. I want to download just the filtered submissions. I don't want to download all submissions. is there any way to do that ? 

https://www.drupal.org/project/content_parser

When starting the parser module, I get an error.

InvalidArgumentException: sink must not be a boolean in GuzzleHttp\Client->applyOptions() (line 384 of /home/admin/web/testdr.vpoltave.net/public_html/vendor/guzzlehttp/guzzle/src/Client.php).