I have a 2005 545 with an SMG transmission

I was driving yesterday I noticed that my car was slowing down, I gave it more gas but it didn't accelerate. I stopped the car and tried out the different gears. When I had it on 1st and on reverse and gave it gas it barely moved.

I think this is the clutch but I am not completely sure. I'm about to take it to the shop but I would like to know whats wrong so I don't get overcharged.

 

No any warning or indicator?

When engine got overheated, this would happen, usually....

 

Sounds like an SMG gear selection sensor. Have a seat, its going to be a long ride!