It's stuck since 5 days in it's seed hul...

You need to remove that seed shell. It can't do much until you do. Best way with with 2 small tweezers or 1 tweezer and something like a toothpick. Trick is to hold half the shell steady so it does not transfer any streses to the seedling. Then, gently pry the other half of shell open with the toothpick. IF done right, the seelding will not move or get damaged in any way. Hold the shell steady, and all is well. If after removing the shell a membrane remains, don't try to rip that off. Slide it off the end of the cotyledons. Gently push it with the toothpick. It will slide right off. Again, secure the seedling if you can so you don't transfer any force to the seedling. It shouldn't be twisted, bent or bending while doing either of these things... easy to avoid damaging it if you do it right. I find some extra strong reading glasses help a lot. You do this a few times and you don't even think about it. If it happens often, sow the seed a it deeper. I'm fine with about 10% coming out with a shell for the sake of faster sprout times, but each to their own deciding what is best in that regard. That's how i've adjusted to avoid it... keep it to 1 our of ten or less and still get ~3day sprout time average.