Passcode for screen time enabled. I have no kids

To reset the Screen Time password on your personal iPhone follow these steps:

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1. Open the Settings app, then tap Screen Time. 
2. Tap Manage Screen Time. 
3. Tap Change Screen Time Passcode, then tap Change Screen Time Passcode again. If asked, enter the Apple Account email address and password that you used to set up the Screen Time passcode.
4. Enter a new Screen Time passcode, then enter it again to confirm. 

It’s recommended that you don’t skip adding a Screen Time Passcode Recovery. That way, if you forget your Screen Time passcode, you can use your Apple Account to reset it. If you have more than one Apple Account, you must use the same account you entered when you set up the Screen Time Passcode Recovery. 

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copied from: Change your Screen Time passcode on an iPhone or iPad - Apple Support

After that you can disable Screen Time completely in the Settings for Screen Time.

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1. Go to the Settings app  on your iPhone.
2. Tap Screen Time, then do any of the following:

• • Turn off Screen Time: Tap Manage Screen Time, then tap Turn Off App & Website Activity.
  • Turn off your Screen Time schedule: Tap Screen Time Schedule, then turn off Schedule.
  • Turn off your Time Allowances for apps: Tap Time Allowances, tap Manage Categories, select a category, then select Delete (your category name) Category.

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copied from: Set up Screen Time for yourself on iPhone - Apple Support