Welcome to Apple Support Communities quivadise,
We can definitely understand needing to updating your MacBook Air and want to help. From our understanding, you Mac is stuck at "less than a minute remaining" but doesn't provide any type of error message is that right?
You mentioned restarting your Mac, have you tried restarting it in safe mode to see if the update will install? Check out: How to use safe mode on your Mac.
If this continues, you may want to reach out to Apple Support for further assistance. Depending on your region, you may be able to reach out to them here: Get Support.
Have a good one!