100% agree with the guys.
I suspect the 'stiffness' encountered on your take-down lever is caused by a 'newer' unfitted take-down spring.
I say this because at manufacture this Luger was a fully functioning armorer fitted Luger ... over time small parts are replaced by hobbyists but NOT fitted.
If you are handy at 'gun smithing' the solution I have found is removing the spring and cleaning the springs seat in the frame.
Try it again.
If it is still stiff you will need to gently file the top of the spring with a jewelers file.
Do not be aggressive with the file and check frequently for proper 'fit & feel' of the take-down lever.
I have done many of these springs.
These springs are prone to breaking so ere on the side of caution but don't stress if you break it ... springs run around $0.25 for generic to $25.00 for an original in Canada.
The most frustrating part is reassembling the take-down lever back into the frame which sometimes goes really easy but more often than not can try your patience ... after you have done a few and picked up some assembly experience it becomes very easy.
Whatever you do DO NOT force fit the lever into the frame ... you can end up breaking the lever.
You got the lever out so you know you can get it back in BUT it demands 'exact' positioning with a small amount of force to reassemble it
If you are having difficulty refitting your lever set it down and walk away for a bit.
Frustration is the enemy of the gunsmith.
PS: I love your gun ... it's a beauty.
