Theme development

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.

Looking for some advice for a Noob please.

I created a sub-theme of Varbase and am using it with mixed success.  It looks great but I am having trouble with some basics re-theming the site.  I try to edit some files and either the gulp does not pick them up or it does, but the class attributes I added don't end up in the final html.

If someone could help with two basic questions. 

I created a subtheme using the starterkit and have changed all instances of 'THEMENAME', everything works but the theme settings are all blank. I cleared the cache too but nothing appears.

The options are still there because I can click on things, I just can't see them.

https://i.ibb.co/yp1cN5r/alalalal.png

Thanks in advance!