a stone dropped from the top of a cliff received ground in 4 second and burries itself at 0.8 meter into mud.calculate height and retardation.

How does a stone "receive" ground? Do you mean "reach" ground?

How do you define "retardation"? The backwards drag fiorce in mud?

The height H that the stone falls in time t is
H = (g/2)*t^2

H = 4.9*16 = 78.4 meters