"I saw my students last year."
The thing is that at the point we're talking about - one year ago - her living in New York was an ongoing state. In fact 住 is an inherently stative verb and is therefore hardly ever used together with 了 (and when it is, it's the sentence-final "change of state" 了, not the "completed action" 了). Skmilar verbs include 知道, feeling verbs such as 喜欢, as well as all adjectives.
By contrast "I saw her" views you seeing her as a completed action in the past. If you were talking about the past state of you seeing her, you would use progressive and say "I was seeing her" (in English that also happens to idiomatically mean that you were going out, but let's ignore that because it's not relevant here).
From the context there is no way to tell if this sentence is perfect or imperfect. "I was seeing my students last year" would indicate that the action is still ongoing. "I did see my students last year" would indicate that the action is completed. Also there is no indication if there is one or more student.
It is true that 学生 is basically 'student'. One thing I have figured out from this course is: Words like this can be used as plurals. Just like 医生 in the course, sometimes it is 'doctor' and sometimes 'doctors'. I guess we can only learn by enough exposure to the written language.
No, you can use it for nouns as well. Only nouns which refer to people (so no *桌子们 or something), but that’s the case here. Still, it is only used very infrequently for nouns. For one thing, it pretty much always implies definiteness. So 学生们 sounds like we’re talking about a particular group of students we already heard about, not about some unknown students, and certainly not students in general. In our sentence above, the students are indeed definite (a possessive makes things definite), so you can say 我的学生们. But it’s not required at all. It’s very common to not use an overt plural marker if it’s not absolutely required to hammer down that there are indeed multiple people.
That's true, but the english sentence is ambiguous then: "I saw my students last year" could mean either.
It's tough too because "I met my students last year" is ambiguous between "I met (with) my students" and "I met (for the first time) my students", which other sentences want to see as 见 and 认识
去年 （qù nián）= last year
今年 （jīn nián）= this year
明年 （míng nián）= next year
昨日/昨天 (zuó rì/zuó tiān) = yesterday
今日/今天 (jīn rì/jīn tiān) = today
明日/明天 (míng rì/míng tiān) = tomorrow
上周/上(个)星期 (shàng zhōu/shàng gè xīng qī) = last week
下周/下(个)星期 (xià zhōu/xià gè xīng qī)= next week
作 zuò means “to make, to compose” (among other things); it has nothing to do with “last year”. I assume you meant the character 昨 zuó instead (note the tone difference in their readings too)? This morpheme (word part) specifically refers to “yesterday”; it can’t be combined with other time words besides 天 or 日 to more generally refer to “last/previous x”. “Last year” is 去年 qùnián (literally: “the year that has left”; 去 used to mean “to leave” in Classical Chinese). It’s just a fixed word.
That one is definitely wrong. 些 is a measureword, corresponding fairly closely to English “couple; bit” as in “a couple of students, a bit of milk”. It is never used as a noun suffix to indicate plural. The only plural suffix in Chinese (Standard Mandarin Chinese at least) is 们, but it’s only ever used for people, and even then it’s is optional in most cases. You can use it if you really want to stress that you’re talking about a plural noun, but most of the time information plurality either doesn’t really matter for understanding what the speaker wants to say, or already clear from context/other parts of the sentence so 们 is not needed. So 我去年看见了我的学生 could be talking about one student or multiple, we don’t know. Maybe the speaker is going to tell us down the line, or maybe not, in which case it probably wasn’t important.
Firstly the rule of the game in Duo is to be literal and do not change the word order, although Duo would surprise you occasionally.
The time element in a Chinese is usually either at the beginning of a sentence, or in the middle before the verb; It is never placed at the end, so avoid it.
What I find with Duo is that sometimes it is literal and sometimes not. With the Chinese some of the answers they recommend are just not literal or direct translation. I find guessing is a horrible way to learn because getting answers wrong out of not knowing why undermines confidence. I've done 15 lessons so far but this one is a bit crazy and overly complicated compared to the others. Duo is great to practice with, but it would be much better if it gave you an explanatory lesson in the first place before it throws you in the deep end where the only way to survive is to learn answers off by memory, and not understand the grammar or the 'why'.
Pity because it's about 90 % there otherwise and could be the best on the market.