The confirmation cannot be deleted

What causes this issue?

You want to delete a confirmation in a purchase order or in a
scheduling agreement.
This is not possible, becuase a goods receipt has already been posted
for the confirmation you are trying to delete <ZH>and</> this
confirmation type is planned for a <DS:DE.WEZUO>GR assignment</>
<ZH>Note</>
You can only delete a confirmation with a GR assignment when no goods
receipt has been posted for it.

System Response

How to fix this error?

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.