How do i walk through something but also be able to stand ontop

so recently Ive been working on a game with a tree jumping system similar to shindo’s
and i decided i wanted to make tree physics similar to theirs.
so i tried looking up about how i could do this and i found a video about
collision groups
which showed group id 5 as the one i needed,
so i eventually tried this and nothing worked,
i couldn’t walk through it.
so how exactly would one do this??
here is an example of how it works:

https://gyazo.com/c3778ac2ff881c5ee83e35e4eb397aea

You could enable CanCollide if the HumanoidRootPart's Y position is higher than the part