Greetings, CoJo07.
It appears that you're unable to restart your MacBook Pro. You can turn it off and on using the power button, but not from the menu. You also mention that the update won't complete, and we're glad to help with this.
See if you're able to locate the install application in your Application folder or Launch Pad. If it's there, move it to the Trash and empty it. See if your MacBook Pro will restart. If it won't, restart it manually.
How to reset the SMC of your Mac - Apple Support -- Depending on which type of MacBook Pro you own, reset the system management controller (SMC). See if your Mac will restart now. If it does, restart the update.
How to reinstall macOS from macOS Recovery - Apple Support -- If you're still unable to restart your Mac, turn it off manually. Then use the Option>Command>R keys to start in macOS Recovery. This will update your MacBook Pro to the latest macOS that's compatible.
Let us know how that goes.
Take care.