2012 BMW 528XI

My BMW started leaking fluid 4 months ago. Lights on dash came on one light was the triangle light which engine light. I had it serviced completely oil & filter change hooked up to machine that checks all components senors everything checked out great. One week later I was driving I was coming to a stop my brakes sounded like they were grinding next day had mechanic check the brakes all good. Next day I am pulling out of Attorney Parking lot as I am turning the steering wheel my BMW makes a load screaming cracking noise so I turn my steering wheel up right to drive straight it makes the same noise. I stop to look around my vehicle to see if anything is leaking or dragging nothing was dragging but maybe one or drops of something I touched the solution to feel if it was water or oil? It felt oily so I drove to my mechanic he lifted it up on the racks. We both could see some solution was leaking around possibly where engine oil plug is then we saw it had been leaking back to middle of my vehicle water area and running back to the middle of my vehicle. My mechanic decided to put the machine that checks for certain items on vehicles I know it checks my sensors not sure what else?? He and a couple of the other mechanic stop and help him. I left my vehicle he let me drive his vehicle home he wanted to check other issue tomorrow. Next day I got to the mechanic he said he knew it needed a transfer case and 4 sensors he said it would take time to buy a new transfer case for 2012 BMW 528I xl so to leave my vehicle with him.Then I get this letter today 12/13/24 from BMW DATED 10/2024 it states there defect which relates to motor vehicle safety issue which means a part is being recalled on my vehicle!! My question my vehicle has already gotten damaged by this recall I am trying to fix the problems plus paid already $1500. For repairs to my mechanic whom thought that fix my issue but has not. Please inform me as to what I the owner of this model vehicle that has a defective part