Instructions how to create/copy/configure/run dlakelan Gamer QoS script (or any script)

I am having a problem editing the script have tried vi and nano

Hello everyone, everything ok?

Does this script still work fine? I'm using OpenWRT 21, is it compatible?

Do I have to uninstall Luci-SQM-Cake/FqCodel to install this? Or can they coexist?

I want to try to improve my experience playing MW3/Warzone 2.

I would like to take this opportunity to thank the user dlakelan for his effort and dedication.