my iphone could not restored an unknown error occurred (11)

See this Apple article: iOS update and restore errors

iOS update and restore errors – Apple Support (UK)

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Check your hardware

If you see error 53, use these steps.

If you see one of the errors below, you may have a hardware issue:

• 1, 3, 11, 12, 13, 16
• 20, 21, 23, 26, 27, 28, 29, 34, 35, 36, 37, 40, 56
• 1002, 1004, 1011, 1012, 1014, 1667, 1669

Here's what to check. Try again after each step:

1. If iTunes is already open, quit and reopen it.
2. Check your third-party security software.
3. Make sure your USB cable, computer and network are reliable. Then try twice more to restore your device.
4. Check for outdated or modified software. 

If you still see the error, contact Apple Support.