It might sounds weird but i need to slowdown game for one player (movement, ui, physics, sounds, etc.) but his slowness should be visible to EVERYONE else.
slowing down movement & physics for one player is pretty easy, because you can set the workspace.Gravity & the player’s walkspeed locally, and their movements will replicate
(if you do set their gravity lower, though, any physics object they interact with will have low gravity too, see network ownership)
as far as ui & sounds go, that mostly depends on however you have them set up in your game.
if you have a centralized “sound player” module, then you can fairly easily slow down every sound played.
although, if you aren’t replicating sounds manually(you probably aren’t?) you will have to detect when sounds are added/played locally and slow them down
i’m not sure if you intend for the slowed-down player’s sounds to be slow for everybody else, and with any of the methods i mentioned their speed does not replicate(but if you do manually replicate sounds, it’s pretty easy to have them do that)