You were very close! If you mean the French name Feilfaux, it is usually pronounced roughly FAY-foh.
Say it in two parts:
- FAY, like the word “day” with an F.
- foh, rhyming with “go.”
So it sounds like FAY-foh, rather than “feel-i-foe.” French names can be tricky because some written letters are silent. If this is a particular person’s name, though, their own pronunciation is the best one to follow.