There's an easy way to tell Farsi and Arabic apart based on just learning the alphabet somewhat, and that's that Farsi has a handful of letters that Arabic doesn't. It's a bit like identifying French based on the fact that there are é and ç in the words. It won't be 100% foolproof -- a given text might not happen to contain any of those letters, especially if it's short -- but it's a good rule of thumb for an initial sort. If something contains چ (which will also show up without that bottom hook, but anything with three dots underneath it is an instant giveaway) or گ (note the line over top of it) or ends with a letter that looks like ک (Arabic has that letter, but uses a different shape of it at the end of a word), you know it's not Arabic.
Note that Urdu also uses the Persian alphabet. In looking at the sample Urdu text on wikipedia, and the poetry samples just above, what strikes me is all those little backward hooks at the ends of words, which I've never seen in any Arabic word. (It looks like it's a modified ی, maybe?) But that might just be a font choice thing. Anyway, it sounds like you run into Urdu less often.
(You could also run it by me if you want, as triage before passing it on to a coworker's mom. I've forgotten a whole lot of my college Arabic over the years, and my dialect knowledge was never great, but unless we're talking about one or two words, "does this look like it's got generally Arabic patterns and the usual standard prepositions" should still be well within my grasp.)
Alas, I'm no help on Duolingo advice; I've used it to practice a language I learned previously a few times, but it super doesn't work for me as a language learning method. I know it has Arabic, at any rate. There are also a bunch of learn-the-Arabic-alphabet apps, which I know because I found a lot of them when I tried and failed to find a more intermediate app for (re)learning the language.
no subject
Note that Urdu also uses the Persian alphabet. In looking at the sample Urdu text on wikipedia, and the poetry samples just above, what strikes me is all those little backward hooks at the ends of words, which I've never seen in any Arabic word. (It looks like it's a modified ی, maybe?) But that might just be a font choice thing. Anyway, it sounds like you run into Urdu less often.
(You could also run it by me if you want, as triage before passing it on to a coworker's mom. I've forgotten a whole lot of my college Arabic over the years, and my dialect knowledge was never great, but unless we're talking about one or two words, "does this look like it's got generally Arabic patterns and the usual standard prepositions" should still be well within my grasp.)
Alas, I'm no help on Duolingo advice; I've used it to practice a language I learned previously a few times, but it super doesn't work for me as a language learning method. I know it has Arabic, at any rate. There are also a bunch of learn-the-Arabic-alphabet apps, which I know because I found a lot of them when I tried and failed to find a more intermediate app for (re)learning the language.