Both Basic and weighted smoothing stopped suddenly working for me yesterday and i have no idea why. They now behave like the normal Freehand Tool. Is there any way to fix this? I tried to reset Krita, even de- and reinstall it, but nothing.

You could try to reset Krita's settings: https://docs.krita.org/KritaFAQ#Resetti ... figuration

Still behaves like the normal non-smoothed ones, only Stabilizer is working however i don't really like that in comparsion to the weighted smoothing. It's also rather weird HOW it decided to stop functioning, i had Krita open and i worked with the Setting before on a sketch, after a break i wanted to start doing the actual lineart and there it was.