Out of three "Witcher" dubbing variants, as it comes to "[expletive]" and "hmm", where expletive is one of:

Kurwa (PL) https://www.youtube.com/watch?v=_A-_44pRM4U
Fuck (EN) https://www.youtube.com/watch?v=Se5pnYyYs_k
Zaraza (RU) https://www.youtube.com/watch?v=kbTi_5aNJR8

The PL one is the best, just hear it for yourself.