Screen brightness not working

Hello, I just bought a new dell inspiron 15 5000 gaming laptop, at first I didn't have any problem with it, but now the brightness is always on 0 and I cant increase it. every thing in the display adapters is updated and I don't know if its relevant but in the monitor section it has a danger sign on it.
can you please help me????:(upload_2018-9-25_18-34-39.png
 
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