This is part of the limp home mode that has been built into the galaxy/sharan etc. When your brake lights fail to work the car thinks that your brake may be faulty so it turns on the fog lights for protection, there is nothing worse than a car with no brake lights working. There is too switches under the dash that the brake pedal is controlling, the first is for the brake light and the second is for the limp home mode. Now if they replaced the brake light switch which is self adjusting it might have adjusted a little too much and won't switch on. Remove the bottom panel that covers the brake pedal and try and re-adjust the switch till you can get the lights working again, its not easy and not much room. If this dosn't work remove the switch connect it back onto the wiring harness and manually work the switch while checking if the brake lights come on, if not replace the switch, if it does work pull the top part of the switch ( the moving part ) out to the last you will hear a few clicks and re-intsall.