This regulation is not so complicated: the speed signal from the speedometer sensor will be received by the control unit (location: behind the glove box) and is used to control the pressure valve in a power steering system.
This pressure valve allows oil to flow past the plungers of the power steering valve to create a resistance force in steering. Because the steering wheel must return to neutral after turning.
A large amount of oil behind the plunger produces a high resistance force, against which you must apply a lot of force when controlling, a small amount of oil creates a small resistance force - so, the control is carried out easily. And how much oil "counters" here is determined by the above-mentioned valve.
Malfunctions in the power steering system
If the electric power steering is faulty, you can drive the vehicle in the same way as a car with a normal mechanical power steering. But to be sure, check the fuses and the power supply to the control unit. Between terminals "2" and "7" in the plug-in block, the measuring device with the ignition on should show a battery voltage of 12 volts. If nothing happens, carry out further checks in auto repair shops.
If the steering wheel effort increases when turning in one direction, the cause is in the steering mechanism.
[Information obtained from this resource: AudiManual]