I think it has to do with the order of the adjectives.
Even in English in fact, the order of the adjectives makes a difference. If we are to analyze this:
a weird new room = a weird (new room).
a new weird room = a new (weird room).
As you can see in the first one the room is new, but it is weird as being one of its kind.
In the second instance, it is a weird room but a new one of its kind (from a set of weird rooms).
the order of the adjectives in Arabic is the reverse of that in English as well.
I agree with you here however this has been true for all the other examples and duo has not been strict about this, so why for this example. A pretty new house ....a new pretty house. Also when natives speak english, they don't stick to this rule rigidly... the default would be to assume it's just one new weird room by itself, so any new comer to the "weird room" scenario would always check "so is this the only weird room we have?".... (if it was important that is Lol!).
I think the inconsistencies in the answers is majorly attributed to the various contributors of the course, who do not have (apparently) any coordination among them.
Anyway, I'm not sure about other examples here - there had been other sentences with consecutive adjectives here and I've seen people struggling with the same problem of order of adjectives and I've replied there with the same logic.
The simplest and most obvious form of such adjectives can be seen clearly in nationalities: A German American man is not the same as An American German man. In cases other than that, natives might indeed change the order and not being sensitive about it, and we as speakers of Arabic would do the same in many aspects of the language in our dialects nowadays - but the basic and the logic is supposed to be what is to be, and it is supposed to be what to be taught by any course here I suppose. In fact one of the things that I've nagged about a year or so when this course started is merging dialect and standard, but looking now at the progress and how people tend to think and try to learn, I do really think this course could have done better with a dialect instead of mixing the dialect(s) and the standard language (what I would call Traveler's Arabic).
This said, I'm not saying Duolingo is an angel or does not bear mistakes; In fact this course here is a disastrous one compared to others I've been learning here, and I've faced such frustrating aspects that almost made me quit learning any language here altogether (e.g. in Russian, mixing ш and щ would make the WHOLE sentence wrong; Yes, for one letter only the whole sentence is marked wrong, despite natives saying it should be considered a typo and passed on). Yet, away from Duolingo and its problems, I'm simply stating how the logic of the language goes and what is supposed to be the order in this aspect.
This is called Tanwin or Nunation. The (t) part is part of the original word however. The Tanwin is a type of vowel which maybe in ancient times was nasal but then developed to be a full (N) sound. Tanwin can be in 3 flavors: -an, -in, -un; Depends on the status of the word in the sentence. Duolingo, for some reasons beyond my comprehension does not show or use the marker for such a vowel. However, it is typically a double stroke above (-an) or below (-in) the letter, while (-un) can be written as double Dhammah on the letter but the common shorthand is this symbol:
which I hope is clear here.
Thanks for youtr reply. At the beginning, I thought I did not hear well but then I could not help listening to the -n sound at the end of words! So as far as I understood, this is like a declination of a name. According to the logic status of the word in the sentence, either subject or object or a indirect object, we have a different termination of words. I also searched a bit online and found out that this is not common anymore in the spoken language but only in formal texts like the Koran. So now I am a bit confused on the use of such phenomenon since Duolingo uses it.
Well, first of all, Duolingo is not a "pure" course. They made it as a mix of things. Something like a traveler's Arabic to get you going when you need to. There are a lot of mistakes in the audio (because it is produced by a speech machine across the course and not spoken by real people) and sometimes dialectical expressions and words are used instead.
For the Tanwin, yes, it is not spelled out in the daily dialect except maybe in some instances when a speaker would borrow something from the standard Arabic (or FusHá as we call it). People are split here as to whether this course should be for the standard Arabic, or for a dialect Arabic. Personally, I'm a pro to the first one. However, this course is not a good one for standard Arabic but it would be a good start. People who are pro-dialect learning, prefer this because this is what you are going to use with people, but they neglect one important fact: What dialect you are supposed to study? How to write it? No dialect across the Arab world has an "official" status. The official language is simply put "Arabic". One country, can have up to 2 and more dialects. Egypt for example, as I can remember now, would have up to 4 dialects across the land, from North to Sinai and down to the farmlands. And there is no standard writing suited for any dialect after all. Besides, we don't deal with dialects as "real" or separate languages; Some people would give an example that the Darija dialect of Morocco (Morocco alone has maybe 3 dialects beside the Amazight language which has an official status) and they might say that people from the East don't understand Darija, and hence Darija would be considered a language on its own, but this is not exactly the case. We don't understand mainly because of the speed they speak it with and for some of the loan words from French and Spanish and of course Amazight, but in slow manner I am personally able to understand much of it and it even contains classical Arabic expressions that we, on the East, ceased to use.
In a nutshell, standard Arabic opens the door to learning "sub-strata" and it is the official one in use in newspapers, workplaces, ads (although now they are on a hype on using dialect for ads which I quite despise).
And I've forgot to say this in my previous response: The Nunation or Tanwin, can be considered (at a basic level at least) similar to the indefinite article (a/an) in English. Thus, you cannot see a noun with (AL) and Tanwin at the same time; This sounds quite weird for a native. Thus, when a noun is not to be defined, AL is removed, and Tanwin takes over its end. Be careful though, sometimes translating from English into Arabic would not be exact with the definite articles. Example: in English you would say (I love nature) as a general statement, where (nature) here is not really defined (because it cannot be counted at this instance). However, in Arabic, the translation would be: أحب الطبيعة (uHibbu Al-Tabee3ah)m literally (I love THE nature). This is because the ideology in Arabic is that a general concept is supposed to be defined because it is a well-known general concept to the speaker and the listener. Hope this elaborates more.
If you want to learn a dialect, probably being with people of that dialect would help better. There are courses online as far as i know teaching "Egyptian" or "Lebanese" or even "Syrian" - what they mean is just the dialect used in the capitals. For a standard Arabic, Duolingo can be a good starting point. Later on though I'm pretty sure Duolingo won't do much to improve the "sense of the language". This is what I've been through in my Irish learning and now again with Russian, German and Turkish. Mistakes in the content are spread over Duolingo in all languages I think, at least in my case. Standard Arabic is supposedly to be understood by anyone across the Arab world even though it is not spoken on a daily basis because it is taught in schools. Anyway, that's another long story actually.