Introduction of new idioms and phrases
In my opinion, Duolingo really needs a better way to introduce idioms and so on.
When a new word is introduced, it is highlighted in gold to let the user know that it is a new word (or word form) to learn and that there is no expectation for them to know it already. Similarly, new grammatical features such as using different articles in different cases are shown to the user in a sort of speech bubble. There is however no such indication for new phrases, which can make some questions, especially those which are very idiomatic, impossible to answer without "peeking". Since Duolingo encourages users not to "peek", it is at best a little unfair to not let them know it is OK to do so.
As an example, I was just presented with the German phrase „Das geht auf Dauer nicht“. On their own, I know at least to some degree what all of those words mean, but knowing the meanings of the individual words simply isn't enough in this case. The best I could come up with was some gibberish along the lines of "That doesn't go on the duration". As it turns out, „auf Dauer“ translates as "in the long run", but without "peeking" I had no way to know that. It wouldn't be that bad if Duolingo didn't sometimes ask questions where the "correct" answer (or in some cases even the question) was something similarly nonsensical, so making the user wonder "Am I being stupid, is Duolingo asking for gibberish again or is this some new phrase/idiom that I haven't come across yet?"
My solution to this issue would be to do something similar as that which is currently done with new words, but with a different colour (say, purple), such that parts of a new phrase/idiom are highlighted in a similar manner to new words. Duolingo already has a way of recognising phrases/idioms such that when a user hovers over them the suggestions displayed are for the phrase/idiom rather than for the individual words, so I don't see any reason why this wouldn't already be the case. If Duolingo considers things like plurals and conjugations to be distinct enough to warrant a "new word" highlight then in my opinion idiomatic phrases certainly deserve something similar.
EDIT: There's another group which can be added to this: German separable verbs. When the prefix of a German separable verb appears at the end of a sentence (as is usually the case), Duolingo treats the two parts as if they are two separate words, just like it does with fixed phrases. This can be especially frustrating when doing a section on, for example, adverbs, only to be asked a question where Duolingo has mistaken a separated prefix for an adverb (or whatever might be relevant to the current section). Just like the phrases, Duolingo knows that the separable verb is there, and the hints say as much, but it doesn't give the user any indication of that fact.
im learning spanish which i will be using in spain only. im wondering if theres any point in learning the phrases that duolingo gives you to "sound like a native" since most common sayings are idioms and idioms are generally country specific. so if i go spouting off south american idioms will they just think im bonkers?