Overheating will cause lag and will eventually shuts down your laptop. Maybe your laptop is not meant for heavy tasks or games as they demand adequate resources for optimal performance running at acceptable temperature. Its possible to run them but you're putting more stress generally. If it happened just recently then maybe you will have to clean your laptop, because chances are dusts and dirt are piling up inside your exhaust blocking air ventilation preventing your laptop to cool.
Or start fresh and reformat, everything will be snappy.