Isn't "بَيت مُمتاز" supposed to be pronounced "baytun mumtaaz" instead of "bayt mumtaaz"? In the case of "بَيت كَبير" Duolingo pronounces it as "baytun kabiir" and not as "bayt kabiir".
We happen to have in both cases an nominative indefinite noun. So, normally if we follow the grammar rules of formal MSA "بيت" should be pronounced with an "un" in both cases, right?
The reason they're using nunation sometimes but not other times is to show us what the two different types of speech sound like, so that we will be familiar with both. At first, I was frustrated too, until I realized what they were doing. I bought a college text book that is doing the same thing Duolingo is doing; mixing MSA with a regional dialect. The introduction of the book explained that the use of different styles (registers), and even the mixing of different styles in a conversation, is how people actually speak.
No. "Mumtaaz" means "excellent".
If you do your lessons on a computer, there is a "Tips" section at the beginning of every lesson that explains grammar. The "Tips" section is not available on all of the apps, however. One of the "Tips" sections explains that in Arabic, unlike English, adjectives come after the nouns they modify. So, in the phrase "bayt mumtaaz", "bayt" is "house".
If you are doing your lessons on an app that does not have the Tips section, you can access Duolingo on the computer function of your cell phone, or just read the Tips on a computer. Also, if you put your cursor over the words, or press on them on a cell phone, you will see the definition of the words.
This is where you learn it. A few wrong answers are not the end of the world if the goal to using duolingo is learning, and not just earning XP. Further explanations can be found in the lesson accompanying each Skill. Those can sometimes be seen in the mobile versions, depending on the course, but always on the web browser version. :)
I fail to see a reason not to. First they teach us the basics, then words would be introduced. They start with western-ish names and words, then switch to arabic words.
BTW, some of the 'jibberish' sounds we were taught previously were actual words. We were simply not given the meaning at that point because the focus is to teach phonetics. With some know-how we are now ready to steadily switch to words and then to sentences, while learning the rest of the writing system.
Duolingo doesn't always introduce new words with little pictures; which is easy to do with nouns but difficult, if not impossible, to do with adverbs, adjectives, and prepositions. When you're given a new sentence, put your mouse cursor over the words to see their meaning. That's how the new words are usually taught.