Firstly, I'm from Germany, and I love Oovium. I still have a version of it installed on my iPod Touch, but that thing is around five years old and still running iOS... 4.1? Or something? I think? Anyway, it's definitely outdated. Oovium is still the best calculating app I ever found anywhere - though the first few minutes were rather frustrating, so the biggest hint to give is to take some spare time and play around with it for a while... instead of trying to get a grip on it while under time pressure.
Still, as you can probably guess by my latest iAnything-product being several years old, I've switched to Android, so there's that. I'm still looking for anything that compares to Oovium there, so far unsuccessful.
Oh, and about translations? I generally prefer using the English version. Sure, some apps have good, even great translations... but others read like something that makes Google Translate sound like Shakespeare... or Goethe, in this case. So, I don't care if something's translated - at best, it makes no difference, at worst, I can actually use the English version better.