How to overrides some variables of SCSS(PrimeFlex)?

Question

I'm using PrimeFlex in an angular application, with SCSS everywhere. They mentions here that to customize their own scss values, I should clone their repo, modify the variables, and reference the build result.

But since I'm referencing their scss(and not their CSS), would it be possible for me to provide some modified values for some variable?

My goal is to change the breakpoint values.

I've tried the following, without much luck:

$sm:600px;
$md:960px;
$lg:1280px;
$xl:1920px;
@import 'primeflex/primeflex.scss';

Thanks