And I have learnt only German and French. The Spanish ones I know, because my sister learnt Spanish and I was curious about the numbers. But this was about 6 or 7 years ago and actually I hadn't write them until now. So I'm proud of myself! :)
But yes, "fuenf" SHOULD be accepted, because that's how you write a word with an umlaut, if you can't type an umlaut. It is always correct to substitute an E instead.
--I've never studied French xD