Broken propshaft centre

My name is Patrick, I am in France, my car is an RS3 8V 2017 60,000km.
When dismantling my shaft to mount a down pipe I made the mistake of putting my shaft in the middle. I really can't put it back together, could someone explain to me exactly how to put it back together? or place the balls on the cage inside or on the pinion? and what action should be taken to save my tree. thanks in advance.

Notoriously bad to try to fix once removed with no care.
Usually a 2 person job to remove a prop shaft because of the middle bearing race and how easily it can fall apart once disturbed.


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