cannot restore my phone iphone 5s (16gb) - getting error message known erorr (-1). wanted to instal ios8.1

Hello UKBIRO2015,

Thank you for using Apple Support Communities.

I see you are unable to update your iPhone. If you are trying to update over the air, I would suggest trying to use iTunes via Wi-Fi, see this article:

Sync your iPhone, iPad and iPod touch with iTunes using Wi-Fi - Apple Support

If you are still getting the same errors, you may want to see the following article:

Get help with iOS update and restore errors - Apple Support

That article provides the following regarding that error:

Check for hardware issues

Related errors: 1, 3, 11, 12, 13, 14, 16, 20, 21, 23, 26, 27, 28, 29, 34, 35, 36, 37, 40, 1002, 1004, 1011, 1012, 1014, 1667, or 1669.

These errors mean that your device or computer might have a hardware issue that stops the update or restore from completing.

Check that your security software and settings aren't blocking your device from communicating with the Apple update server.

Then try to restore your iOS device two more times while connected with a cable, computer, and network you know are good.

Make sure that your security software and settings are allowing communication between your device and update servers.

If you still see the error message when you update or restore, contact Apple support.

Regards,
Jeff D.

At this time you cannot update to iOS 8.1 if your iPhone supports iOS 8.2. Apple only supports updating to the most recent version of the iOS that the device supports.