video card to replace old amd radeon rx 580 for dell inspiron 5675

First of all, I'm not technical, so please forgive my ignorance of how to describe my situation. 

I know, this is a five-year-old system. But money is very short.
Things started a long time ago with an error on startup with the CPU fan. It's been looked at a long time ago, and I was simply told: Wrong region (I purchased in the USA and am living in Costa Rica), so the warranty doesn't cover the Ryzen 7 CPU.
So the fan has been running at full speed almost since I bought the PC back in 2018. Makes it sound like a jet getting ready for take-off...

Anyway, recently the ability to do anything graphical with my computer has been getting tighter and tighter.
For instance, some games on Steam will simply kill the system. The PC just switches off. No time to even see on the hardware monitor app I'm running if it's a heat peak. But the biggest suspect is the GPU.
Also, I'm now getting a green screen to black to noise flicker on the right monitor.
It has to be the video card.
I just got a professional cleaning, even got rid of the secondary 2TB hard drive which was not working, and got a second SSD.
But my ability to do anything with the computer is getting slimmer by the minute.

The best advice I've gotten is: get a new system. But I just can't afford it.
I want a last attempt at changing the video card. But this PCI express seems to be very specific (proprietary), so I don't even know if I could use the same model knowing that it could be the wrong connection.

So what I'm looking for is advice on what cheap card I could get for it to replace my 8mb Radeon Rx 580 and still have a dual monitor output (even better if both ports are HDMI and not DVI).

I know I'm asking a lot for such an old system.

Am I at the point of having to trash it?

Thanks for any help!