Responsive 3-column component using CSS flex box

This is my second CSS/HTML challenge and I began to feel more comfortable using CSS flexbox and playing around with its properties. Unlike the first project, I took time to think about the steps of implementation of each element and really started to see the whole card changing from a blank to a skeleton and finally full-fledged in much faster pace. It was definitely a great experience!

I'm not if I was following the best practice in terms of HTML semantic or whether I used too many class selectors in CSS. Any feedback is highly appreciated!