Kann es sein das meine Pflanzen länger brauchen als von Hersteller angegeben?

Yeah, breeders guideline is a ballpark at best. There are far too many factors that play into the real world results (temperatures, humidity/VPD, light intensity, light spectrum, plant size, and a whole bunch of other things..) Not to mention there are different phenotypes with every strain. Can have 2 seeds from same breeder and same pack that end up polar opposites of each other. I have had heavy indica and heavy sativa plants come from same pack of same strain. One finished in 8 weeks other was 11, breeder pack said 9-10.. So long story short yes, it's perfectly fine for plant to finish up earlier or later than claimed. You're looking good, keep it up.

If the trichomes are not yet 2/3 brown/orange across the whole plant, then I would just leave them standing a bit longer. Plants are individuals too ;-)