Computer Overheating Issue

Clean the the your cpu mother bord ,proceesor colling fan

I'd like to think its the CPU cooler. Corsair is my recommendation. In my opinion they make the best liquid cooling units. Thermal paste replacement should also fix the issue assuming you've had this build for a lengthy amount of time.

By the way 76 degrees Celsius is perfectly fine for a computer while under a gaming load. As long as your temps are under 90 degrees there is literally nothing to worry about, and even then it will just automatically thermal throttle till it has settled, but you wouldn't want it to be thermal throttling anyways. Also you don't need anything apart from a stock cooler if you aren't overclocked. If you really don't want your temps to be 76 degrees, which are good temps under load in my opinion, get a Hyper 212 evo cooler, you 100% don't need a liquid cooler on a non overclocked CPU.

I think the first question that should be answered is what fan do you have on your CPU? If you are running stock, that might be the reason why. In which case, I would recommend either the Cryorig H7 (much better than the standard 212 Evo everyone recommends) or a liquid cooler. It also depends on your average ambient temperature. If you're running around 90°F, you might want to invest in a liquid cooler as the ambient air wouldn't be ideal for cooling your system.

It would also depend on what types of games you play and tasks you do. If they are heavily CPU intensive, like Arma or something, then you might need a better cooler and the same with workstation tasks like rendering.

Overall, the 76°C is nothing about which you need to worry. I know it may seem high, but similarly to what KJ said, it's fine. I would clean out the computer and then diagnose your problems again.

If it's a laptop I'd suggest you buy a cooling pad/mat to put under it.