Since yesterday I'm playing around with the organ of a local church, I've the feeling that the keys of the organ, which can be pressed down very easily, were ruining my piano technique/touch, is this quite possible or just my subjective feeling?
The organ does require a different keyboard touch - but it depends heavily on the type of organ, the traction mechanism, and on whether you use couplings. Personally I have found that playing organ is not bad for my piano playing. Quite the contrary, it seems.
Just accept that they are different instruments, calling for different music and different playing. Worst thing you can do is play the organ as a pianist, or vice versa. If you are serious about organ playing, get a teacher asap before you learn it all wrong. It seems unlikely that one day of fooling around on the organ is already ruining your piano technique
An electrical organ keyboard (some pipe organs have these) is considered by most people bad for your technique, as a digital piano is for your piano technique.
What organ is it BTW ? Do you have free access to it ?