did you read the explanation?
for one thing, you should be able to tell that your answer is waaaaaay off because there's no way it should take that much of a strong base to still have that acidic a pH.
also, HF doesn't dissociate completely, so where you did HF --> H+ + F- isn't exactly true. while those ions are floating around, you still have a bit of regular ol' HF floating around with it too.
i'm sorry if this didn't help much, but the explanation pretty much er, explains it all!