I have a error and can’t backup icloud.

Hi Eduard_,

Thanks for using Apple Support Communities. We understand you're unable to backup your device, and we're happy to look into this with you. The alert you're seeing indicates that there isn't enough iCloud space to complete a backup. We understand you may only currently be using 1GB of space, but your backup may be larger. To start, check the size of your next backup. You can find that in Settings > [Your Name] > iCloud > iCloud Backup > [Your Device] > Next Backup Size

If you need to manage your iCloud space, you can see how to do so here: Manage your iCloud storage - Apple Support

Thanks.