Vector3 Expected but got number, need help on my custom movement! How do I fix it?

This is just testing. Everytime I play it says Vector3 Expected got number

self.Update = function(position)
        --Forward
        local Position = Vector3.new(0,0,0)
        self.UpdatePosition = Position;

        if self.forward == true then
            Position = Position + self.Forward * Speed
        else
            return;
        end
        --Backwards

        if self.backward == true then
            Position = Position - self.Forward * Speed
        else
            return;
        end
        --left

        if self.left == true then
            Position = Position + self.Sideways * Speed
        else
            return;
        end
        --Right

        if self.right == true then
            Position = (Position - self.Sideways * Speed)
        else
            return;
        end
    end