i have 50G icloud storage using 27.9G but icloud backup not working msg says not enough storage

Hi Macy7,

welcome to the Apple (user-to-user) Community!

You may want to check the storage on your iPhone to see how many Gb the back-up needs.

(Eg: It is likely to be more than the 23.1 Gb you have left in iCloud)

See: How to check the storage on your iPhone and iPad - Apple Support

If there is a computer handy you may want to save an iPhone back-up to that:

Eg: How to back up - Apple Support

It is also wise to: Archive or make copies of the information you store in iCloud - Apple Support

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Else: iCloud is mainly a sync service so your data can be accessed online and from various devices:

You may want to free up storage in iCloud by deleting content that you're not using:

See how to make space in iCloud: Manage your iCloud storage - Apple Support

More info on what you can do: If you can't back up to iCloud - Apple Support

All the best :-)