What if the dealership can't fix your X5?
 

Somehow the dealership can't figure out the problem
Of my X5. Do they seek help from expert technicians
From Germany?

If they think that you'll be willing to pay them for the time required, they can open a PUMA case.

What can't they fix?

Engine stalling, jerking when driven like loss of power. They can't figure it out.

Did they tell you what troubleshooting they have done? Does it happen all the time or is it intermittent? How long has it been going on? More than 1 tank of fuel?

Year/model/engine/trans/odometer?

A post like this w/o year/model etc. info is unlikely to receive help...

2002 X5 3.0 it's been going on for 3-4 months now, it's just getting worse
Where in it happens everytime you drive it. Even on a full tank of gas. Tried it with the
Ac on or off and it still jerks.

The worse part is there's no check engine light
on. Does not shown on the OBC.

The BMW techs there are only as smart as their scanner. Troubleshooting skills take time to develop. If they can't record while driving, it can be very hard to find electrical issues.
What has been replaced during maintenance over the years? I've seen a few other vehicles stall when hot. Usually an intermittent cam sensor is to blame. Either wiring or gunk building up.

O.P.,

You gave people partial info.
What is the trans and odometer reading and service records?