Updated the phone and now it won't turn on or off

Updated phone overnight and now it has a message stuck on the screen saying :

No valid operating system could be found.the device will not boot..

Visit this linkon another device:

www.nokia.com/ mobile-support

ID:A00000P660261301165

Press power button to power off

Anyway press power button and it does not go off screen is actively stuck on ..how can I correct this issue please ,nokiaG50