Browser can't find/doesn't display fonts

@siebenstein There are several ways to customize a theme. Have a look at Customization in the Grav docs. It shows the different options.

The quick and dirty way for testing:

  • Add the font files In /user/themes/quark/fonts
    For example Monoton-Regular.ttf
  • Add the following in /user/themes/quark/css/custom.css
    @font-face {
      font-family: 'Monoton';
      font-style: normal;
      font-weight: 400;
      src: local('Monoton'), url(../fonts/Monoton-Regular.ttf);
    }
    h1 {
        font-family: 'Monoton', cursive;
    } 
    

Refresh the browser and have look.

Of course this should be done in a child theme of quark. See the docs on Theme Inheritance for step-by-step tutorial.