BMW of Fairxfax Car not repaired properly Fairfax, Virginia

I had an Issue that began with my BMW X5 not starting, I towed the car to BMW of Sterling, they diagnosed the problem and determined that issue is related to fuel pump $1500 later they claimed that issue was resolved, however the self leveling suspension inactive error started showing on the dashboard, I took it back to them and learned that they now need to replace a computer board. 

At that point,  I started losing trust in that dealer, so I took it to BMW of Fairfax.  After diagnosing the problem,  they claimed that Sterling's diagnostics were incorrect and that issue was related to the alternator. I had insisted that they determine the root cause before repairing or attempting to work on the car since I was considering the possibility of not fixing it. By then I had already started losing faith in BMW and its dealers. Now another $ down the drain and few days later,  the light/error came back on. I took l it back to them and explained that issue is still not resolved. They kept the car for few days and called me to inform me that maybe the problem is related to pressure accumulator valve, costing additional $1200 & maybe it might not be the problem. 

I told them, to please not fix it ant that I was picking up the car.  When I got there, the car was not only in worse condition , but it was not even drive-able anymore .   I was going to return the loaner, to pick up my car, simple step that should only have taken 30 minutes max.  They held me there, back & forth for 3 hours!!!   I am now forced to fix the car because of the irresponsibility & negligence.   

They now claimed that issue is related to possibly pressure accumulator valve as mentioned above and if that does not fix it, issue might also be related to other components. They have computer logs that they claim to be viewing and still cannot tell me what is wrong, instead proposing different parts and few thousand dollars later I learn that issue is not fixed.  When I confronted them with the facts and demanded to speak to the manager, I was told there is nothing they can do, and now since the car is not in driving condition, I have no choice but to leave the car with the dealer again for further repair and MAYBE just maybe after spending few more thousand dollars get it repaired.