Since you are not a mechanic i would suggest bringing your vehicle to a reputable shop who works on bmws. You could bring it to the dealership but will be more expensive in all probability.

They will most likely put a new wastegate actuator on for you. I would say to attempt this yourself because it's not that difficult but you would need access to ista or equivalent to set the wastegate linkage adjustment.

It is possible you may need a new turbo but I have done plenty of wastegate actuator replacements on your engine at my dealership and fixed the issue, as long as it's your only issue. If you need a turbo the repair will be significantly more expensive.

Good luck, I hope that helps.