Pay attention to his time in the game. Record x, where x represents the name of your presentation. Enter stop at last, or exit directly. Then go to the cstrike (English) or cstrike_schinese (Chinese) folder and find the X.dem just now.
Next, enter the game, build a map casually, go in, enter playdemo X on the host, and then enter the movie 20 or 30, depending on your speed. Numbers 20 and 30 represent the number of frames of the screenshot.
Then you can see many pictures in the cstrike (English) or cstrike_schinese (Chinese) folder. Just use a simple video production tool to make these pictures into videos. More troublesome.
I suggest you record the demo directly and send it to the administrator. General administrators know how to judge whether a player cheats or not from a demo.