why volt is needed for calculate watt?
high voltage will not cause to the electrons to move faster


Voltage does cause electrons to move, and all else being equal, higher voltage causes electrons to move faster.

If you could put a Coulomb of electric charge* into an electric field of one volt per meter, then there would be a 1 Newton force between the field and the charge.  If you pushed that charge one meter into the direction of the field, you would have put 1 Joule of potential energy into it -- and the voltage would have changed by one volt.  If you did all that in one second, then you would have had a one Ampere current across a one volt gain -- and you would have exerted one Joule in one second.  So your one Joule in one second is a Watt of power, and your one Ampere across one volt is, again, a watt of power.