2nd Screen Low Resolution

I have a problem on my pc: my 2nd screen just got a low resolution and I have no idea how to fix it. The internet tells me all kinds of things I don't understand so if someone knows how to fix this and explain it so I can fix it myself, I'd be very thankful.

I have tried pulling the cables out and in, and trying to fix the res in the configuration screen, but that didn't work.

 

You've tried the steps in this help article? https://support.microsoft.com/en-us/help/14108/windows-7-change-screen-resolution

Also, has the monitor always done this or is it a recent change?

 

It has always done that, but only sometimes when I started up the computer, but now it happens randomly.