The brief
The CLA200 had developed squealing, grinding and scraping noises when braking. He brought it in before the braking performance dropped further, which it does once those noises start. Those sounds come from worn brakes: the squeal is the wear indicator on the pads touching the disc, and the grinding and scraping mean the pads are past that point and the discs are worn unevenly or thin. Brakes are a wear item, and there's no nursing them past the indicator, so when they get to that point the rotors and pads go together, because fitting fresh pads onto a worn disc just beds them into the same uneven surface. Ignoring brake noises only leads to more damage and worse stopping.
The diagnosis
Wheels off, the front pads were down to the wear indicator and the discs had reached their minimum thickness, with a lip worn around the edge. Fitting new pads onto worn discs doesn't make sense, so it was a set job, front rotors and pads together, to reset the braking properly.
The work
The front callipers came off, the worn discs were swapped for new genuine Mercedes-spec rotors, and a fresh set of pads went in. The slider pins were cleaned and greased so the callipers float freely, everything reassembled to torque, and the brakes bedded in on a controlled road test, a series of measured stops to lay an even layer of pad material onto the new discs. The road test confirmed the squeal, the grind and the scrape were gone, the pedal was firm, and the bite was back.
The outcome
No squeal, grind or scrape, a firm pedal, and full, even bite back at the front. The CLA200 went home with the braking reset to like-new. Brakes are a wear item and there's no nursing them past the indicator, so doing the rotors and pads together gave the car back proper, confident stopping power.