Möglche sources of error:
poor reception (WLAN), download over the wireless network, low battery
If everything does not arrive, you should the device restart.
Have a new iPhone 6. Have this morning an update via WLAN started but stopped because I had to go and now I try it with iTunes, there is but "20 hours left" and this will not change for the time being not much: - / know someone advice?
Go to a location with good wireless reception + fast internet. If necessary, times to restart the phone. Alternatively, you can import the laptop the update also via iTunes.
You could try all cancel by keeping your screenshot key around 30 sec are holding down and then release lässt.Müsste actually work