It really depends way more on how you drive than how much time passes. I have a car that I use a lot in the city with tons of traffic lights and all that, and I can tell you the pads wear out pretty fast compared to when I hit the highway. If you brake a lot, if you're constantly on the pedal, or if you're one of those people who slams on the brakes at the last second, obviously they wear out faster. In your case with a 2019 Ibiza driving in the city, the shop telling you they're pretty worn is completely normal, doesn't mean you did anything wrong.
What some people mention about 40,000 to 70,000 kilometers is a ballpark range but pretty variable. Some cars last longer, others less. It depends on the weight of the vehicle, the type of pads it came with from the factory, the quality of the brakes overall, and mainly how you drive. If you brake smoothly, anticipating what's coming, they clearly last longer than if you're constantly pressing the pedal. The city is brutal on brake pads, everybody knows that.
The important thing now is if the shop tells you they're pretty worn, better replace them. It's not something you should ignore. When they wear down a lot it affects your braking and plus you start damaging the rotors, which is way more expensive to fix. It's not a job that's expensive or complicated, so just get it done.