My Galaxy S4 won't turn on ! What can i do ?

I've put my phone to charge overnight. I woke up yesterday morning and tried to turn it on but it won't ! I've tried every solution i found :
-Switching the battery
-Holding the power and the volume buttons
-Removing and putting back the battery
-Let the phone charge for a while
-Removing the battery and clicking on the power button.

NOTHING worked ! And this is the second time this happens. It happened 3 months ago and the solutions worked !
Please please help me i have important things on it.

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