GPU not showin in device manager

First thing is you shouldnt have to disable the gpu after playing a game. If its getting too hot then you have a cooling issue. Second, the blue screen is most likely from overheating, theres a chance its something else although I highly doubt it. What we can do is simply reinstall the GPU driver. Or, if you want to get to the root of the issue, we can find the source of the blue screen. I'll need you to get the error code from the blue screen. The easiest way to do that would be for you to download AppCrashView Nirsofts appcrashreport. And then kick me back the error number. If you dont want to download anything we can use event viewer. I can walk you through how to find it in there if you want. All up to you, the easiest option would be to just download the driver but in my opinion it will only get you to the next time the pc crashes so you might as well figure out why then see what you can do to fix it.