Hello Martin. This should be something that you can do yourself. Most likely the bulb has worn out for the low beam. Purchase one from your local dealer as aftermarket parts could cause problems on your vehicle. (It is possible that a helpful service writer won't mind popping it in for you either as our dealership does this all the time.) If you are going to install the bulb yourself it is not too difficult for the low beam replacement(if you have a blinker out this will have to be done at the dealersip as the headlamp needs to be removed on an x5 for the blinker bulb)
Turn on the lights and do a quick check to make sure which one is out, left or right or you could replace both since if one is out then most of the time the other is not too far behind. Make sure you turn off the headlights before you replace the failed bulb. I am going to include different repair instructions. As I am not sure of the options on your vehicle just refer to the one that matches your vehicles lighing. Let me know if you need further assistace.Thank you.
Most of the time you will not have to remove anything even though it is listed in the instructions and the bulb can be accesed through the vehicles components.If you are having trouble the headlight assembly can be loosened by the two 8mm bolts on top of the headlight and then there are two hidden bolts down inside the engine area that can be accessed with a long extension.Then the headlight can be pulled out a bit for ease of installation.I will include those instructions as well.
This is the picture of the 8mm bolts.
BMW Mechanic
Level 1 BMW Master Certification, 9 Years Dealer experience, Team Leader, Shop Foreman