how fast does game time pass?

[King Bogs]

how fast is normal, fast and fastest in irl time?

[Shidan]

Normal is approximately 1 in-game minute every 2 irl seconds. While fast is x2 speed, and fastest is x5 speed.

That said, the speed varies based on performance. Generally speaking it gets slower and slower over time, as the game does more things and drags performance down. But in an ideal world with no lag or performance issues, it would be 2 secs per minute.