Question

what happened to the capacitance of a capacitor when we place a conductor between
them

Answer 1

between the plates of the capacitor or what?

Answer 2

Is the conductor connected to the plates? Or just in the middle?

Answer 3

it will act as a resistance
or any other conductor

Answer 4

If the conductor touches both plates of the capacitor, then the capacitor cannot hold any charge and so the effective capacitance will drop to zero. C = Q/V = 0/V = 0.