iMac (probably 2009-2013) 27" screen goes from white to black when boot up

I tried to fix up a boot problem where iMac stopped to load (loading bar stopped to move). First I booted to safemode to fix the bootdisc but it didn't help, it said the disc should be fine. Then I googled little bit more and found this NVRAM reset possibility by pressin alt+command+p+r after reboot and after that I got this real problem.

Now when I start my iMac, it first gives me the chime, then white screen shows up and then it goes black or the screen goes off completely but rest of the machine keeps running. It won't even show the apple logo anymore nor the loading screen. I can't even boot to safemode anymore or atleast Im not sure because the screen goes completely black.

Any ideas what wen't wrong and how I could go back to the situation where the screen still worked? I don't think I broke it in any physical way so I think there should be some sort of a solution for this.