I add a CSS file (mymovies.css) to a custom form (SeenMovies) in a custom module (eric) with this code I inserted at the end of `buildForm`

    $form['#attached']['library'][] = 'eric/mymovies';

and this code in `eric.libraries.yml`

    mymovies:
      version: 1.x
      css:
        theme:
          css/mymovies.css: {}

But my css doesn't override `bootstrap.min.css` as you can see in Firefox inspector:  
[![enter image description here][1]][1]

How can I fix that?
  [1]: https://i.sstatic.net/Kxp3S.png