That's just an image of where and what a video card looks like. It's not the same card you have. The blue video port in that image looks like VGA, but VGA isn't listed as a port on the GTX 1080. Your monitor doesn't even have a VGA port so I don't know how you'd connect it that way. The XPS 8930 does have both an onboard Intel Graphics HDMI port and a DP port. But with a video card installed, you should use a port on that card. Assuming the monitor has an On-Screen Display (OSD), open that by pressing button(s) on the monitor itself and confirm that (a) it's set to use DisplayPort and its resolution is set to "Native/Recommended". Also, open the Win 10 Display screen. Confirm Resolution is set to "Recommended". Then on same screen, if "Scale and Layout"  isn't set to "100% (Recommended)" set it that way and see what happens with the games. If necessary, try other settings for Scale/Layout. You can also go to the Win 10 Ease of Access screen and adjust "Make Text Bigger" and "Make Everything Bigger." and if that helps. And after opening a game press Alt-Enter and see what that does...    
You're going to get sick of hearing from me, but here I am again. I've had Dell computers for over 20 years, and they've all been excellent. Then, my boyfriend spent $4000 on an XPS 8930 system, and I've had multiple problems, including: It was set up incorrectly at Dell, prior to my receiving it. I sent it back; Dell admitted the fault was theirs; and, upon having the tower returned to me, it was better, but not "fixed," in my opinion. The Dell logo never did show up during boot, and I couldn't get into the BIOS. (There is a reason that's important to me.) After twice getting no boot at all, Dell sent an onsite technician, who was very good and very nice. He found a faulty SSD (which Dell had presumably worked on not long before) and a faulty motherboard. He replaced them both; finally, and I could see the Dell logo upon boot. It seemed that all was well. But, gradually, the boot became slower, again not showing the Dell logo, but showing the following messages: Scanning for signal; no signal from your mDP device; entering sleep mode. Then, finally, the desktop shows a signal from my mDP device, and everything works fine after that. My problem is this: the warranty service (which we paid for) runs out in 40 days, and it seems that essentially the same problem is going to continue: If the Dell logo shows, it will gradually stop showing; boot will get slower, until the machine won't boot at all. Then I'll be sitting here with a $4000 coat rack or something. Basically, I'm afraid there's another problem with the motherboard or the SSD, and I don't know what to do. The reason I'm desperate to see the Dell logo is that I want to be able to get into the BIOS, to ready myself for the possibility of another SSD failure. If I can get into the BIOS, I can migrate the OS to the HDD, and possibly be able to keep using the computer that way. But I'm afraid either the motherboard or the SSD will fail again, and I won't be able to try to rescue the computer. Thanks for any hints.
XPS 8930, recurring problem