Hello weatherstrip sunroof seal ( I marked in the photo)
the seal is plastic or is just old ? because mine is very hard and is very easy to break it like in the picture.
Should this seal be soft ? I mean when car was brand new the seal was rubber and soft ?

That seal should be soft.

My current sunroof is in the same shape as yours: very brittle, breaks off a little more every time I remove it. I just found one at a salvage yard a couple weekends ago that still has the soft seal, completely intact. At least in my car's case, when it was repainted quite a few years back, the painter did not remove nor tape off the seal. So the paint hardened on the seal and it started deteriorating from there. Hope that helps!