"Many people speak Chinese."
Translation:Moni ihminen puhuu kiinaa.
Paljon is "much", and moni is "many" People in this context can be counted/quantified, so "moni" would seem more appropriate.
However, I am still undertain why in this case, the Finnish syntax calls for 3rd person singular conjugation puhuu, and not plural puhuvat because of the pluralized subject.
Moni ihminen has a plural meaning, but is grammatically singular. Kind of like 'many a person'. The plural form would be monet ihmiset.
The verb matches the grammatical number. So 'moni ihminen puhuu', but 'monet ihmiset puhuvat'. I suspect either would be coherent in this sentence.
Monta is partitive singular, while ihmisiä is partitive plural. They need to match, like 'monta ihmistä' or 'monia ihmisiä'.
Genitive singular would be 'monen ihmisen', genitive plural 'monien ihmisien/ihmisten'
The subject is most often nominative, like moni ihminen. I think I've only seen Duolingo use partitive monta as the subject in existential and possessive sentences, like 'Lähellä kasvaa monta suurta kuusta.'
Existential sentences have a location, a verb, and the subject. Possessive sentences are the same, but the location is the possessor, and the verb is always on.
Just my guess but I think you are comlicating this simply because you have yet to teach the plural. You should do so or drop these singular examples while insisting that they are somehow plural. It is axiomatic that you don't teach pe[ple things they will have to unlearn later.
'Moni ihminen puhuu kiinaa' is grammatical, correct Finnish. It's not something that will need to be unlearned later.
'Moni has a plural meaning, but is grammatically a singular adjective. And an attributive adjective needs to match the noun's case and number, so ihminen is also singular. And then the verb is singular.
Singular moni ihminen puhuu is somewhat like English 'many a person speaks'.
You could also use plural monet ihmiset puhuvat. Plural adjective, plural noun, plural verb. According to Wiktionary, singular moni is more formal, plural monet more informal.
This course is teaching written Finnish, not one of the colloquial spoken dialects, so perhaps that contributed to the decision to use singular moni.
I don't know if you've encountered it yet, but muutama, 'a few', is also a singular adjective that's followed by a singular noun and verb.
I believe in another discussion you said you were using the app, and that there were no tips. Trying to learn without any explanations would be frustrating for me.
Moni is introduced in the tips here.