iPhone storage full

1.

Try to free up iPhone device storage see this Apple articles below:

If you need more space for an update on your iPhone, iPad, or iPod touch

If you need more space for an update on your iPhone, iPad, or iPod touch - Apple Support

How to check the storage on your iPhone, iPad and iPod touch

How to check the storage on your iPhone, iPad and iPod touch – Apple Support (UK)

Clear Other storage on your iPhone or iPad

Clear Other storage on your iPhone or iPad - Apple Support

2. 

If you wish, you can upgrade the 5 GB free iCloud.

See -> What's the difference between device storage and iCloud storage?

What's the difference between device storage and iCloud storage? - Apple Support

See also the following Apple articles:

Upgrade to iCloud+ -> Upgrade to iCloud+ - Apple Support

iCloud+ plans and pricing -> iCloud+ plans and pricing - Apple Support

How to use iCloud on iPhone -> How to use iCloud on iPhone – Apple Support (UK)

Manage your iCloud storage -> Manage your iCloud storage - Apple Support

Sometimes it helps to backup, erase the phone and then restore the backup. If you have a computer that you can use, that would be the ideal way to go because you will be able to download a fresh copy of the iOS software. If you don’t have a computer, you can still erase the phone and restore a backup, but the software will not be downloaded and installed again.

How to backup your phone.

How to back up your iPhone, iPad, and iPod touch - Apple Support

Restore iPhone to factory settings

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

Restore iOS backup

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Be sure to restart phone after deletions. If that doesn't help, you will need to make further deletions.