My Lenovo IdeaPad Y580 laptop seems to be having performance problems recently. I used to be able to play FarCry 3 on high settings with ~30 fps, but now, I'm only getting ~15 fps on low.
This all started after an incident that was caused by me putting my laptop in "High Performance" power mode (where the laptop does not hibernate) and putting it in it's laptop sleeve without turning it off. I know that it wasn't the smartest move (at all), but I was only planing for it to be there for about half an hour. Unfortunately, I forgot about it and didn't take it out for about 4 hours later. It felt ~120° F. which isn't that bad, considering that I live in Texas, but what worries me is that it couldn't ventilate or something.
Regardless, the performance hit only occurs in this game, but every other function of the laptop seems to be working perfectly. It is completely possible that no damage was done and it might be due to something else, but I don't see what else it could have been. Right now with only basic functions, Speccy, and Chrome open, it is running at ~55° C and the fan is constantly running, but not a full power.
Now for the questions:
How could I check if my laptop is over heated?
If that is the case, is there an alternative way to fix it than to replace it?
What else could be causing my problems?
Is it possible that there is dust inside that could be causing the problem?