Problem solved, with the help of a knowledgeable
sales consultant - service technicians were clueless.
By default, VW Polo and Golf don't have pressure sensors mounted in the tires. The computer can detect lower pressure the same way as a skidding wheel while braking: ABS detects the speed at which each wheel is turning. A faster turning wheel in normal driving conditions indicates that the wheel is slightly smaller in circumference than the others, which can happen if its pressure has decreased.
It's easy to find out if you have air pressure sensors: they are part of the air valve, and use the external part of the valve as a radio transmitting antenna. Therefore, this external part must be metallic. If it's a simple rubber valve, you don't have an air pressure sensor.
Thanks for reading, hope this helps! Tonight I'm getting the car fixed in less than 30 minutes