QR Code Page Using Flexbox

Hello, I've tried my best to recreate this webpage. This is my very first project and I have a few things I'm not satisfied with and would love to receive feedbacks on

1. My container's still bigger than I wanted it to be, what's the best solution to make it smaller?
2. The blue background of the qr code has 2 shadows which I have no idea what it's called and how to do it. I'm happy to receive feedbacks on any other things too. Thank you!