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Voilà je peut plu prendre de photo la cemera ver moi la touche qui permet de retourner la caméras à disparu de mes aplie
Here I can not take a picture of the camera to me the key that allows to return the camera to disappeared from my aplie - GT
Hi @Licorne, sorry to hear about this. 
Your question has been translated to English as this is an International forum.
I'm not quite sure that I understand your question completely, is the button to change back to the back camera not available in the camera UI?
You can try and clear data for the camera application and see if that helps. To do this, go to Settings > Apps > Camera > Storage > Clear data > OK. This will not delete any photos or videos, it will only reset the camera settings.
Let me know if that helps and I'm sorry if I misunderstood your question.