Hi @Jessy19, sorry to hear about your phone. 
You question have been translated to English since this is an English only forum. Feel free to use a translator to translate my answer to your local language if needed! 
Where you doing anything specific in the phone when this occurred, for example used an application or service?
I'd recommend that you start with holding down the power button and volume up button at the same time for 10 seconds. This will force the phone to shut down and you will receive 3 short vibrations > power the phone on again with the power button.
If there is no change, open up the cover for the SD card and use the tip of a pen or a similar object > press and hold the OFF button for 10 seconds, you will receive a couple of vibrations now as well > power on the device with the power button.
Let me know if that helps!
Hi @CelenieWTSSE, I'm glad to hear that it worked for you!
I hope this won't occur again in your and if it does, keep monitoring when it occurs, if you were using a specific application or service in the phone.
Let me know if there is anything else I may assist you with!
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