You report "my pc frozen crashes after 5 minutes gaming ". This may be a system lockup, where the laptop becomes unresponsive and must be reset, rather than an unexpected shutdown due to overheating, where the laptop just dies like someone pulled the plug. It's important to determine which problem you are trying to resolve.
Load up HWINFO64 andconfigure it to log CPU and GPU temperatures. When your laptop freezes or shuts down unexpectedly while gaming, you can then restart, open the HWINFO64 log file, and you'll see what the temperatures were just before shutdown.
Even though overheating is a common cause of unexpected shutdowns, you want to confirm it's taking place, so you know you're addressing the true cause of your problem. A faulty power supply can also cause unexpected shutdowns. It may also reveal your lockup is not related to thermal shutdown.
Monitoring temperatures will also help determine if your cleaning efforts reduce temperatures enough to avoid a repaste.
G74SX-A1 - stock hardware - BIOS 202 - 2nd Monitor VISIO VF551XVT