Mobile-first solution using CSS and Flexbox

Hello everyone, this is my very first Frontend Mentor solution.

I tried to focus every detail on design as well as I could, and write well structured simple, easy to read code.

Is there simpler, or best-practises to place elements right/bottom corners of their containers? Like images are in this solution.

What is the best way to place info-cards to "cross" formation on desktop screens?

Where you think I did good? What one thing you would change in my code, why, and how?

Thanking in advance Janne