Need buying advice for a high resolution monitor

Hello, I want to buy a new monitor, but I don't know which one.
The things I want:
-A high resolution, the maximum for my graphics card is 2560x1600. I want to utilize it as much as possible.
-the screen doesn't need to be too big, but not too small. I want a good size for sitting around 80-100 cm from my monitor.
-It doesn't need to have a lot of functions like USB and MicroSD slots.
-Paying more than 500 euro for a monitor is the max.
-I would like it if it has the same ratio as an A4 paper because that is more pleasant for your eyes instead a total rectangular display. This isn't 100% necessary.
I hope someone can help me with choosing a new monitor.
Kind regards,
x11.

Gaming, photo editting and writing office documents.

thanks, I will search there, didn't knew them.