How to change header background and link color in Bootstrap subtheme?

Question

Drupal

Created a subtheme based on the Bootstrap theme.

The following code is written in the bootstrap_subtheme.libraries.yml file:

framework:
  css:
    theme:
      css/style.css: {}

The bootstrap_subtheme.info.yml file contains the following code:

libraries-extend:
  bootstrap/framework:
    - bootstrap_subtheme/framework

And along the path my_project\themes\custom\bootstrap_subtheme\css I created a style.css file . But when I wanted to change the background of my header and the text color of the links, nothing changed. I think Drupal uses default styles for the header which prevent me from using my own styles. I even looked at the default stylesheet Drupal uses for my header - navbar.less

How can I change my header's background and link text color? And is it even possible? Or do I need to remove the header region and create my own header in the twig template to be able to style the header?