scripting help

im new to scripting, every time i try what happens in the forge preview is way different to what happens in game…

How do i create objects that despawn every 20 seconds or so at the start if each round (like mongoose sumo)
and how would i create blocks that move up and down at random times, kind of like a whack a mole type movement

any help?

I’d like to know a little more about this too. I’m trying to make a conveyor belt for an Elongation reimagination, but it’s seems really inconsistent even in the preview mode.