Discussion anything about backend engineering

Hi guys, i want to learn about Best-pratice in backend. i have used django and flask. give me suggest about learning a few things

1. I heard 12 factor is the best way to make app.

2. Playing container such as docker and k8s. sometimes make me dizzy

3. i trust clean code. but what difference with oop?

or maybe you could add more...

thank yoy all

regards, Bimo