QR Code - HTML and CSS only

I did not know what to do at first. I thought I had to make the QR code from scratch (noob haha). Anyway, I figured it out soon, and I had fun doing it. I'm happy to learn how to center image vertically using flex.

I'm not sure if what I did in the text part <h2> and <p> are correct. I wanted bigger margins on left and right of the text so their extent would be narrower than the QR code. Margin-left worked, but margin-right had no effect. So I decided to put them in a text-box with a set width instead. Is there a better way to do this?

Also, because I didn't really browse this website, I did not see the note there to try to use tools like SASS. It's the first time I learned of this term, so I have to check it out. But really, why do you have to use those tools? Isn't CSS enough? Why add another step?

Feedback most welcome.

Thank you!