Него is the form of 'его' that is used after prepositions. Н also appears before other similar pronouns as well (у + её = у неё, за + им = за ним).
(However, when его or её means 'his' or 'her', and modify some other noun, then you don't put Н. For example: у его дочери ничего нет 'his daughter doesn't have anything'.)
Is it like a rule, or just one of the styles of language ?
Like in English, you can say "I ain't got nothing", and maybe even a triple negative "I ain't got no nothing". You can understand it from the context. But "I have nothing" is also correct.
Is "I have nothing" INCORRECT in Russian ?
у меня ничего, sounds goofy and incomplete. You will sound kinda like a Russian Tarzan. (which if you are a beginner, it isn't really a big deal really)
Maybe a Russian speaker that knows that you are learning might be able to understand you out of context, but it would be grammatically incorrect.
Is "I have nothing" INCORRECT in Russian ?
«У меня́ есть ничего́» would mean something like "I have nothingness" in the philosophical sense (although the more common way of saying this is «У меня́ есть ничто́»).
I believe "He doesn't have nothing" is considered incorrect in standard English. While some dialects might allow it, Duolingo expects you to stick to more-or-less standard English.
Please note that the translations are mostly entered by Duolingo contributors by hand, so allowing non-standard dialects would require singificantly much more work to prepare a course, because there's a wide variety of different forms. E.g. if we allow "He doesn't have nothing", should we allow "He ain't have nothing"? Maybe "He ain't got nothing"? Maybe "He ain't got no jack", as was suggested in the comments elsewhere?
Given the number of English dialects and varieties, creating a course that allows constructions from all of them would be a very daunting task. That's why this course only allows more-or-less standard varieties, the English that is taught at schools.
That's not what I meant. My problem is with the russian phrase itself. Shouldn't it just be "У него ничего", meaning "he has nothing".
"he doesn't have nothing", although its used in many languages, but is technically incorrect don't you think ?
So why are technically incorrect phrases which should come later on being taught at beginner level here ?
«У него ничего нет» is the correct equivalent of "He doesn't have anything". English considers double negatives incorrect, Russian requires them.
In negative sentences (sentences that use «нет» 'there is no' or «не» 'not'), we also need to use negative pronouns («ничего» 'nothing', «никто» 'nobody') and negative adverbs («никогда» 'never', «нигде» 'nowhere').
In English, you use only one negative word (e.g. "I've never been there" or "I haven't event been there"). In Russian, all the words that can be negative become negative in negative sentences (e.g. «Я никогда не был там»).
Thanks I get it. But there should have been direct translation and mention of these things in the lesson. I'm well aware of the fact that double negatives are used quite often. English also uses double negatives in informal-ish settings, sort of.
So, but my question now is, that does it always have to be a double negative ? "I don't have a house" will always be "I don't have no house" in Russian ?
"I don't have a house" will always be "I don't have no house" in Russian ?
Almost. Since we don't have a direct equivalent of the English negation «no» (just like an article «a»), we only use one negation in this sentence: «У меня нет дома» (literally, "At me (=at my possession) there-is-no house").
However, "I will never tell anybody" will be "I won't never tell nobody": «Я никогда́ никому́ не расскажу́» (I never to-nobody won't tell).
If you don't use negative pronouns, the sentence would just make no sense in Russian. «Я когда́-либо кому́-то не расскажу́» sounds very strange.
Modal verbs are a different can of worms.
Basically, in sentences with modal verbs we can negate two things: the modal verb (can expresses possibility, can't expresses imposibility) and the main verb (have expresses possession, have not expresses absence). And 'it's impossible for one to have anything' (=one can't have anything) is in fact very different thing from 'it's possible for one not to have anything' (=one can have nothing)!
So, this is not really a double negation because different things are negated: -n't negates the modal verb, and 'nothing' negates 'have'. (For the same reason, 'I don't like unnatural sentences' is not a double negation: both don't and un- are negations, but they negate different things.)
In Russian translation of "One can't have nothing", both 'can't' and 'have' will be negated: Ты не мо́жешь ничего́ не име́ть (you NEG can nothing NEG have).
(I've replaced 'one' with 'you', because 'one' would be translated impersonally, without a verb at all: «Нельзя́ ничего́ не име́ть» 'it-is-not-possible nothing not to-have', so it makes a bad example.)
It's an exception. -его is often pronounced as -ево in the end of the word (in rare cases, not just in the end, as in сего́дня).