Not quite. In Italian that's toccare il fondo. The English idiom can also mean that you've started to recover from the low point, in which case it's cominciare a riprendersi o a migliorare.
The recession has finally bottomed out = la recessione ha finalmente toccato il fondo. Sales have bottomed out = le vendite hanno cominciato a riprendersi.
You have arrived at the bottom makes no sense in English unless it is referring to, say, riding an elevator, or hiking down a mountain. You have arrived at last would be a much more common general phrase in conversation. If that is NOT what this means in Italian, then how would you say THAT in Italian, as that seems a more useful phrase to know.