I think i can't tell you because from looking at it the courses are designed by different people and are of different standards.
But no it won't give you any command of a language whatsoever.
Some of the courses seem to be very good and some seem to be very bad. I think it really would depend on what language you need to learn.
On the spanish ...I think it's terrible
for teaching vocab ...but has a use in some way for grammar (but there are some problems there too) . I can't stress this enough. Its VERY VERY basic. You need to be studying more vocab alone.
They just repeat the same vocab over and over. Baby stuff. But at the same time it forgets basic stuff with vocab. (but they probably imagine people are learning on their own too )
I am not saying my spanish is great or anything but i lived there for a year as a kid. Basically the spanish on duolingo is a bit awkward at times. For just one example. They don't use vosotros but ustedes mostly ...which is common in latin america spanish but they use it mostly for formal situations and in latin america ustedes isn't formal but it is in spain. So its wrong for both dialects. They also get some words wrong.
It does some good things though ..its good for drilling your gendering etc ...and drilling grammar when it does get it right. That tends to be something people get wrong a lot.
Terrible for vocab though ...they need to vary that more. Its very repetitive.
I really don't think you will learn to speak a language with this app or gain a command of it. I see it like a brain stimulating game really.
I think alongside classes and time practicing speaking with people etc its a good thing. But alone ...nope. Plus it does teach you mistakes etc as i said by applying rules across the board. It encourages incorrect verb conjugation sometimes.
Sometimes all of the multiple choice questions are wrong ..or awkward ..i just choose the least wrong looking one.
Grammar rules ..aren't rules ...they are the analysis by which a linguist tried to understand a language. And the way by which someone tried to teach it.
You will learn things with it ..but you will also have to UNLEARN things from it. For example when i started i could UNDERSTAND lots of spanish but speaking it ...bit janky ...but when i was LISTENING to spanish ..i didn't translate stuff in my head. Now i find from all the translation exercises to drill grammar on duolingo ..I AM TRANSLATING THE SPANISH TO ENGLISH IN MY HEAD WHEN I LISTEN TO SPANISH NOW
which is a step back.
Second Language acquisition is fascinating tho ..
People expect educational material to be totally correct. However this is not so ...
Why the spanish is awkward ....well i am not a native speaker ....its hard to explain ..but well ..if it wasn't duolingo ..i would assume the sentences presented to me from duolingo were not from a native spanish speaker...they don't correlate with fluency. I don't know how else to say it. Don't take duolingo as an example of fluency.
Also it would say things I know are correct ..were wrong.
Also they SAY they offer both castillian and latino spanish ...but they only offer latino ..the castillian course is latino spanish and the speakers sound mexican ..in a way this is GOOD thing ..because if you want to have a neutral spanish accent mexican spanish is good ...they elongate the vowels and speak slowly ..but you HAVE to understand Castilian because i feel if you can understand castillian you can understand anything ...they speak the fastest spanish imo ...and they shorten and speed up the vowel part of the words it can sound like they are almost only saying the consonants a times.
Duolingo doesn't introduce vocab fast enough. I don't know how much time you are meant to spent on the tree etc but well you don't seem to get a lot of vocab in that time. I mean if you want to be fluent in a language within 4 yrs i think its something like 25 words a day you need to learn.
I honestly think its an app to drill grammar
. But within that paradigm it has a lot
of bugs. Outside of that paradigm its very of VERY limited use.
I actually ended up switching my native langauge on it to spanish so i could see what the english course was like. It has HILAROUS!
I would advice anyone who does duolingo to switch their home language and try their native language course ..you will understand then.
To sum up....it has its place. But no you won't learn to speak a language from it ..it is also teaching you bad grammar too if you are not careful. And it has a lot of instances of bad grammar. I was surprised.
The way it asks questions is weird..or basic.
I would not say its even A1 level DELE.