You have arrived at the bottom would be considered obscene in the UK and parts of the US. Tsk-tsk.
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.
Is this talking about the standings in a race? Or a disgruntled child pointing out that their parent was so late to the school play they missed it entirely?
This sentence could be used if you finished a long race, not about the standing of the race.
Or if you dig in a barrel and you find the bottom.
Could be literal (They have funicule here, so getting to the bottom of it could be literal) or an idiom... or both.
"Come" is now rejected.
Some uses of "arrivare" accept "come", some don't. Duo should either make everything consistent, or explain why not in the discussion.
The mean you propose is correct, but it is not normally used in Italy in this type of context.
A correct context could be "Non e' cosi cattivo in fondo" (He is not so bad after all)
In my opinion in this case the mean is "you are arrived to the bottom".
"nel fondo" literally translate to "in the end". In this question "Sei arrivato nel fondo " translates to "You arrived in the end (eventually).
"You came last" would be a more likely way to express this in English, but Duolingo told me it was wrong!
I put "You arrived at the end" and was accepted. Maybe you arrived at the end of the play and missed it?
"In fondo siamo stati insieme" says in the song "non ti scordar".. In fondo can definitely be used as an idiom meaning -in the end
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.