Very low chance of success.
SS guards typically had flap holsters. It would be very hard to get the flap up and withdraw the pistol of a guard while he is resisting and his fellows are grabbing you.
A better idea would be to use a sharp object like a pen to stab Hitler in the neck or temple. I would try to stab him in the neck behind the jugular vein and pulling back rip the jugular open.
You would likely instantly lose your life. But if it is what you wanted to do try to do the unexpected and something difficult to prevent.
Most of the WW2-vintage German holsters I’ve seen, in addition to the flap, have a pull string — the pistol hits deep in the holster and you pull the cord to make the pistol lift high enough to grab. Quick for the guy wearing the holster but a difficult angle for anyone else teying to extract the gun.