Power on but screen ia black

While i was browsing facebook, tablet screen went black with some vertical grey lines, it has not been dropped. It's chargrd, i've tried several times to restart it, it plays the intro music and the screen lights a little bit but still black, i've tried to press power button with both volume buttons, it restarta but still black screen.

tried again with power button and volume + only once and with volume - once again but never works.

any advises