Yes, what Adam said is correct, it's the nominative indefinite ending, -un, which is rarely written, but if it were, it would be written as بابٌ
Notice how the small symbol above the ب looks like two small وو linked together. The grammar behind when we use what when talking about indefinite things is a bit too involved to explain here, so what I suggest you do is pay really close attention to what you hear while following the Arabic letters with your eyes, and you'll eventually get a feel of what to use when. It takes a long time to acquire this skill, so just be patient and listen to a lot of Arabic while following text every day. You'll get there eventually :-)
When speaking in real-life, nobody actually pronounces the -un sound except news anchors, or during some kind of official speech. Even in school, when reading books out loud, the sound is dropped in more advanced classes. Only children are made to pronounce every single sound. I'm trying the course to test it, and so far, it seems the readings tend to mix between fully reading every sound, and dropping the ones that are normally dropped. This mimics real-life, so it's good to get used to hearing both version, with -un and without it.
Feel free to also copy and paste Arabic sentences into Google Translate and listening to how Google's engine reads them, just to get used to multiple voices. There are several other available voices online as well. Your laptop or phone probably has a built-in one(s) you could use as well. Have fun! :-)
I don't want to discourage you, but it's good to have realistic expectations to be able to conquer a goal, so here is the hard truth: Arabic takes much longer to learn than English or French. Some classifications say that it takes more time than Chinese, and I actually agree with that. Arabic has its rules, but they do tend to be rather involved and require some commitment to study if you really want to master the formal language. There are also several exceptions to the rules. Having said that, it's ok if you make some mistakes that violate strict grammar rules. Native speakers do them too. Just be patient and enjoy learning something different :-)
tough argument you make, I am not sure whether to agree or disagree because you do make a good point.
Technically tho, it is 'wrong' not to have nunation, and it does serve a strong purpose in the language and is one of its essences. Does it make it quite hard? Yes.
In real life many Arabs may not pronounce it but they do acknowledge that they are wrong in not pronouncing it and that they are speaking dialectical or even that their own MSA is influenced by dialectical - that is the key difference (it is not about saying it correct or wrong, but rather about knowing how it should be pronounced right and wrong).
I would recommend at least making a note about nunation at some point, it really is an essential part of Arabic.
Nunation does indeed have a purpose, and in some cases, having the wrong nunation or not having one changes the meaning of the sentence. That's why it is mostly only written in cases that remove disambiguation. When speaking, people would just ask if they misunderstood.
Regarding 'right' and 'wrong', the way I see it, grammar is there to describe language as it is used by people as closely as possible, but it could never fully describe it, as language constantly changes. MSA is an attempt from academics to impose regularity on a language, which doesn't always have it in real-life. There are actually more than one MSA standard even, and they compete based on politics basically.
If you're interested in learning MSA deeply, it's quite interesting and I'd encourage you to do it. But is it essential for you to sound native? Not at all. It's more important for you to work on your listening and pronunciation skills for that.
PS: I am a contributor to another course (German for Arabic speakers), not this one. So I cannot add any of your suggestions to it.
Yes it should if you want to be grammatically accurate, however, we often don't pronounce the last diacritic at the end of a sentence while reading, which is probably why the makers of the course didn't add the final ٌ event though I think it's better for beginners if they add it.
Thanks for noting بَوّابَة (bawwaba). Perhaps that you are not familiar with باب has to do with dialect? It's for sure an Arabic word, albeit through Aramaic (it's a common meaning of the word in Babylonian Aramaic, including Mandaic), and it for sure means "gate." It's a well-known word in the history of Islam on account of the name given to Siyyid ‘Alí-Muhammad, whose remains are now interned on Mount Carmel in Israel (Bahai). On the word itself, see, for instance (the second link refers to "related terms"): https://www.definitions.net/definition/bab-el-mandeb and https://en.wiktionary.org/wiki/باب
This is not making sense. I have gone from learning just letters and sounds to suddenly being expected to translate vocabulary that hasn't even been covered. I'm just expected to know what the words mean now and it hasn't even been introduced yet. Reading sounds is very different to knowing what they actually mean and there's no progression to it.
As benton1 wrote, DL is an inductive learning tool that works best for adult learners who are willing to learn from mistakes and at their own pace. I take it for granted that the learner should also work through a grammar or two and also do immersion experiences if possible at some time. Having said that, each DL language does "scaffolding" differently and some of the languages are at different stages of development. Your input can help DL Arabic scaffold more effectively in some ways.
The words "mumtaaz/excellent/amazing" and "bait/house" are not in this sentence, only "bab(un)/door" and "jadiid/new". The "-un" in called "nunation" and is used to show that the noun is the subject of the sentence in MSA. In MSA the adjective should also have the "-un": Babun jadiidun.