Theme development

Hello!

I am trying to make my own theme, I am a beginner. I installed it, I could set it as default, but, when I enter the site, it says "The website encountered an unexpected error. Please try again later". If I look at the error code in the cosole, it says 'Failed to load resource: the server responded with a status of 500 (500 Service unavailable (with message))'

A picture of the folder:

https://ibb.co/Fg0vchn

Could anyone help me, please?

I have Drupal 9.4.8 and those are my codes:

I've just started on a custom theme extending stable9. The CSS is being loaded properly, but the javascript isn't. The following code is a testing page just to check if the code is working. Is there something I'm missing? The code works when I place it inline but I'd prefer to have it as an external file for good practice. 

My info.yml looks like this: 

Hello, I have question about theming emails. I installed Symfony mailer, because with this module it should be possibel to send themed/html emails. But all emails still look the same like before. Specifically I would like to be able to send formated confirmation emails for Drupal Commerce. Right now all the mail are in simple text format. No matter how hard i try, I am unable to find the solution to send html emails with Symfony mailer. Could you help me?

I am usind Drupla 9.4.8 and Symfony Mailer 1.0.0-beta1

I am using an entity reference field to display author names on our site.  I added a 'published_name' field, and referenced it to the Author taxonomy. The published_name taxonomy field is within the a custom profile called 'Writer Profile', made using the Profile module. The Writer Profile is added as a rendered entity on admin/config/people/accounts/display. The writer profile fields display on the user's profile page, but I would like to do is customize the twig so the writer profile fields are displayed on the user's profile the way I want.

Hello, I need your help. I am building website build on my own theme which contains e-shop (with Commerce v 8.x-2.31). On my local server everything works great, but when I deploy it to my live test server there is error when I try to add payment gateway for eshop.
In log, there is PHP error with this message: