"There is less time than I thought."
Translation:Il y a moins de temps que je ne le pensais.
This an "expletive" (a dummy "ne"), which has no real role in the sentence, other than helping a nice flow of words (to French ears, it sounds quite literary). To be precise, "ne" here does not give a negative meaning to the sentence. In real life, you may say or hear "ne" or not, "le" or not or none of either; the meaning will remain exactly the same.
So I know about this concept and recognize it when I see/hear it. But I don't know when to use it myself and when not. (Or is it so outdated that I shouldn't use it at all and just be happy that I know what it means?)
I was just about to ask if you had any links to elaborate this further but then I realised you already gave us the name. Expletive! And I could now search for myself.
But I only found this: http://french.about.com/od/grammar/a/negation_form_2.htm Where "ne" is explained when used to convey a negative meaning.
Is this what's happening here? Or do you use expletives in more ways?
Expletives are "cosmetic" words, inherited from times where French was an elegant language. Nowadays, only highly educated people (educated in French, of course, not in computer technology) or people who care, actually use it. So, you may use it in sentences you know by heart and forget about other variants. If you are able to understand that it is not negative, then you are safe.
Interestingly, "moins de temps que je pensais" gets a lot more Google hits than any of the variants that Duo deems to be correct.
Peut-être il faut une troisième catégorie "argot" ainsi que "vrai" et "faux". Cette voudrait dire "c'est vraiment comment des gens parler, mais vous semblerez inculte".
The past imperfect is massively used in French but its tense mapping with the English preterit, present perfect and their continuous variants is extremely difficult to draw, in particular when sentences are so short and vocabulary so scarce. On top of it, many English speakers tend use preterit as the past tense (good for everything), so it does not help.
If you ever come across this sentence again, you will not lose a heart if you enter "il y a moins de temps que je croyais/pensais". I added variants to make our lives easier.
My point is that there are several different meanings of the word "think" in English, not all alike. It would be very surprising to me if the French verb "penser" functioned in exactly the same way. As I do more and more of these exercises, my level of trust in Duolingo steadily drops because I continue to see English translations that are non-standard, awkward, or just plain wrong. As a result, I don't have much faith that any particular French phrase is really something that a native speaker would use. So, my questions should always be, "How would a native French speaker really say this?" and/or, "Would it sound strange to a native French speaker if I said it this way?"