My solution

Some feedback:

• you should enhance the semantics of your HTML, by using h1-h6 elements to tag headings, the article element to tag each card and the blockquote element to tag the testimonial text (since it is a quoted text);
• when using @font-face, you can use the WOFF2 format, which compresses TrueType and OpenType fonts (if you want to know how to convert a .ttf file to .woff2, check this article);
• when declaring areas for a grid layout, it is better to use names with semantics in mind: instead of using the first names of the testimonials, use names such as “first” or “last” and, by the way, you can leave some areas unnamed, by using the null token (.);
• even though you used relative units to define font sizes, you used pixels to reset the default font size (_settings.scss, line 26): remember you should always avoid using pixels to define font sizes;
• even though you use SCSS, now you can replace Sass variables by custom properties in most cases.

I hope this feedback helps you.