Translation:It is forbidden to talk on the stairs.
Is in the stairs not correct? It was dans, not sur, so it is more natural to write in for me.
I was marked wrong for saying "it is forbidden to speak 'on' the stair ways" in england this is perfectly normal. It sounds slightly alien to say 'in' the stairways. Im getting sick of these americanisms. Why should i be penalised for my work because some people speak a terrible bastardised version of english?
What you are experiencing is not an Americanism, but a Duoism. Nevertheless, the noun is "stairways", not "stair ways", in any form of English ever heard. Please don't be in a rush to blame the Americans. The issue doubtless stems from the original French word « l'escalier » which may be interpreted as stairway, staircase, or stairwell (or simply "stairs"). In French, on dit "dans l'escalier", but in English the expression would be "on the stairs/stairway" but "IN the stairwell". So, the original translator thought that it must be "in" in all versions of English (not so). The other motive may have been to use "in" so as not to confuse why "dans" is translated as "on". So no matter how you look at it, there are opportunities for people to jump to conclusions and be offended at somebody.
I'm American, and I find the English awkward as well. Duo prefers the most literal translation, not the normal way of saying the same thing in conversational English (of any type). It's the inherent difficulty of learning a language by translating back and forth, rather than by just dialoguing in the one you're learning.