Cancel Huawei update?

The following problem: I have pressed a key combination (both volume keys & key lock). Now my phone makes an update which got stuck at 5%. However, I have no internet (neither wlan nor flat). How can I safely cancel the update without causing further damage?

Canceling will be difficult and I think you do not get around a loss of data.

You could first try a factory reset on the recovery (deletes everything on the internal memory!) http://all4phones.de/huawei-anleitungen-faqs/28664-wie-lassen-sich-huawei-smartphones-android-auf-werkseinstellung-zuruecksetzen.html

If that does not work, you could try flashing a new image (deletes all data as well) https://androidmtk.com/flash-stock-firmware-huawei-smartphone