Obviously there would be a lot of small (not to mention a couple large) changes humans would need to get used to on a planet that rotates much faster than Earth. The biggest one I’m concerned about right now though is how they’d measure a day.
Let’s say that, barring a few incidental adaptations or changes in sleep cycles, this planet’s inhabitants were humans as we know them. If a single 24-hour period on this planet sees three periods of “night” and three of “day”, then how might people start to think about and label this? Would they even attempt to frame it in terms of the 24-hour period Earth humans do, or would they simply accept the new day-night cycle and sleep multiple times in short bursts within 24-hour periods, coming to see a day not as a 24-hour period that’s split by multiple nights, but as a much shorter eight or six hour period of light followed by six to eight hours of darkness? How would they come to see their planet’s natural satellites, if it had any?
To clarify, this is a fantasy world. The humans living in it are, with the usual handwaving and suspension of disbelief, the same as humans in the real world. They’ve lived on this planet all their lives and have no preconceived notions about how time is measured on Earth or any other worlds.