Theme development

Here is the menu.twig.html template provided by Drupal Bootstrap :

I have a navigation menu on my site, each menu link corresponds to a page of views.

I want to display in front of each menu link, a badge with the number of results of the corresponding page views. Like this :

My menu <span class="badge badge-light">4</span>

How to display a result counter in the page menu link ?

https://i.stack.imgur.com/FoqYy.png

I want to change hreflang="en" to hreflang="ro" globally?

How can I do this in using mycustomtheme.theme.THEME file?

Good afternoon!

I am having some slight issues with a new installation of Drupal 8, with bootstrap CDN as my theme config.

Currently I am trying to setup my portfolio to display different menu items on different pages

This is my main nav on my homepage: Home - Contact - Game A - Game B - Forums

If a user clicks on Game A then the top nav will be: Home - Downloads - Maps - Server - Forum

I tried to change the text and position of the error message.
My Drupal version is 8.8.4

In the Drupal standard,
An error message is displayed above the username.
How can I change the position of this message? 

Now I want to display below the submit button. and If possible, it is best to control them in the twig template.

I also want to change this text, and although I can change it, But it looks like there is a problem.
I referred to the links these.

I am upgrading a theme from Drupal 7 to Drupal 8.  I reference .css files in mytheme.library.yml that do not seem to be getting pulled into the site.

I've looked online and even copied sample coding and replace the names appropriately. Yet I do not see them being applied or reference to either .css file, in the source code or Developer Tools.

If these files look correct, then any direction to what could be the cause will be appreciated. If it is permissions, please let me know what permissions it SHOULD be! 

Thank you.