Actuating device for brake system of motor vehicle and method for operating actuating device

The invention relates to an actuating device of a brake system of a motor vehicle and a method for operating the actuating device. The actuation device comprises a master brake cylinder actuation module which can be actuated by a brake pedal assembly and/or an actuation actuator in order to displace a working piston of a master brake cylinder, said master brake cylinder actuation module comprising an actuation module body, an actuator force transmission element is at least partially accommodated in the interior of the actuation module body in an axially movable manner and can be actuated by the actuation actuator, wherein a pedal force transmission element is received at least partially within the actuator force transmission element in an axially movable manner and the pedal force transmission element can be actuated by the brake pedal assembly, and wherein a first sensor detects a displacement difference between the pedal force transmission element and the actuator force transmission element, wherein the sec