How do I get rid of Focus and "Do not disturb"?

You don't. You certainly do not need to use it and should never see a Focus State turning on as long as you have not set a schedule for it. If you are experiencing any trouble with it, then describe what you are seeing and what has not worked that you tried. Screen shots are helpful as long as they do not contain any personal information.

You will find many things that cannot be deleted as they are part of the OS, on both the Mac and iPhone.

Ok, so on your laptop:

• Go to  > System Settings > Focus, and make sure Share Across Devices is turned off. If you have this on, then anytime focus is turned on your iPhone, it will turn on your Laptop.
• Make sure you do not have any Schedule set up at  > System Settings > Focus > Do Not Disturb, and if there is a schedule under Set a Schedule, then tap on it and the remove button.

You are now set to manually control focus and if it is currently showing the moon icon, then click the Control Center in the menubar (slider icon) and click the Focus button (Do Not Disturb will be showing with the moon icon), then Do Not Disturb to turn it off. The moon icon will appear grey for about 5 seconds then will disappear. It can also be done by clicking the moon icon that you see in the menu bar. It should no longer turn back on automatically. The process is similar on the iPhone, and if you need assistance, I can help there as well.