I picked a guide that was supposed to be simple for beginners. It showed how to put the main parts together but said nothing about fans. My PC overheated in ten minutes because I had no airflow. Now I have to order more parts and redo everything. Why do guides leave out such basic stuff?
Yeah, "check the paste" is always solid advice from @the_uma. My own laptop was doing the exact same thing, overheating super fast during games. A fresh tube of paste bought me another couple years, honestly.