25k km for rear pads on a city-driven BMW is actually not unusual. Modern BMWs have a rear-biased brake distribution, meaning the rears do more work than you'd expect.
City driving with lots of stop-and-go is the worst case for brake wear. Highway driving barely touches the pads.
Its normal, nothing wrong with your brakes.
same thing on my wifes X1. rear pads at 28k km. fronts lasted until 55k. the rear bias is real on these cars.
just replace them and dont worry about it. use aftermarket pads like Brembo or ATE - same quality as OEM for half the price.
also check if your parking brake is dragging slightly. the electronic parking brake on the F48 can sometimes not fully release, causing premature rear pad wear. you can check this with ISTA or Bimmercode - look at the parking brake calibration values.
