Thank you for answers,
my monitors does not support DVI, both are VGA.
And multiple display activated. It seems no error with drivers or configurations. But 2nd monitor wont work.
while restarting system, 2nd monitor is allways black. This shows problem is with the hardware.
Repating this part;
on DisplayPort, there is 2 converters serial connected. DisplayPort~DVI, DVI~VGA.