I think I found it, at least the resistance is gone now.
I try to describe it in english, please tell me if it is not understandable.
I "degreed" both u-joints, so that they have the same angle axial. The X of the u-joints are in the same position, so when I turn the steering wheel they move synchronous.
I admit I haven't understood it fully, but it seems to be ok now.
Thank you all for your help!