testimonials-grid-section

From the start, the media query is toooooo big, reduce it to laptop size ( 1021 px ), here you can get more info about common media queries breakpoints

https://cutt.ly/Rlo5upC

second, instead of using "ntchild .class .class" stuff I see on your css, just make a new class bassed on the style you are making.

instead of having that stuff for "color: var(--very-dark-grayish-blue);" make a new class, maybe called "card__body--dark-blue"

for the grid you don't need to use more than 4 1fr or "repeat(4, 1fr)" you'll get a better result.