Hi,
Thanks so much for your report, and welcome to the forum!
The problem has already been reported, but is unfortunately not yet fixed.
Please add your custom styles temporarily in the page settings of your heading template (there it should work, and the correct media queries automatically apply), or in Bricks » Settings » Custom Code » Custom CSS, and add the media queries manually.
I’ll close this thread accordingly, and we’ll update the original thread once the issue is resolved.