Thanks for your help Max!
I managed to set Helios at least to the state that the right MFD works:). But the left and middle MFD and other displays doesn't show anything. The buttons on them work but they don't show the image on them:(.
In the Helios editor, I have everything green in "Interface status", the setting in "Monitor setup" is on the picture, and in DCS I have the resolution set to 1920x2280.
What else should I set, or where am I doing something wrong, so that I can see the image on all MDFs?
Thanks.