Flexbox came in handy, learnt one new technique

I used flexbox for layout. But while I was trying to reduce the browser the width, flex-items were not proportionally decreasing. But I later solved that. I had to remove the card width, but add max-width, min-width, flex-grow to 1. And got that nice feeling that we call happiness. How does it look? Feel free to point one common mistakes or any suggestions will be appreciated. Thank you.