Just to put this in context, any game in which you checkmate your opponent in under 20 moves is considered to be an incredibly quick game, where your opponent must have helped you by playing a really horrible move. The game is over before it has even started to develop. To be checkmated in 9 moves means you basically were making the worst possible move many times.

It would be easy for any marginally skilled chess player [1] to survive 20 moves against even the world champion. If Magnus was specifically playing to checkmate you quickly, 30 moves would be difficult and 40 moves would probably be impossible.

1: ~1500 UCSF strength