"Do not take this, take something else."
Translation:Nie bierz tego, weź coś innego.
why do I have to use a different verb on the second part of the sentence? (bierz x wez)
Why are two different verbs used when the same verb is being conveyed in this sentence? bierz and wez
In imperative, the negative sentences almost always use an imperfective verb ('don't do it at all'), while the positive ones use a perfective one (do it succesfully and completely). That's why it looks like that.
"Niech pani tego nie bierze" (avoiding "tego" at the end, it can be a sentence of its own after all), then in the second clause there's no negation, so it's Accusative "coś innego" and not Genitive. Also in a positive sentence, "bierze" is rather unlikely, it will be "weźmie". Added that.
Because it would be taking something on many occasions, that's rather less likely.
Actually, yes. I look at reports like "nie bierz tego bierz cos innego" (literally two such reports) and I can't imagine this ever being said.
btw this "cos" reminded me about something I've been wondering about: if you get a report that is otherwise correct but the accents are just missing (or some other issue like "dont" instead of "don't") and you accept that answer, how does the system know to "fix" it so that the answer isn't shown to people with "cos" instead of "coś"?
The system doesn't fix anything, I do. By adding it manually. Contrary to what many people seem to think, there isn't any automatic translation or anything like that on Duolingo. Everything is put on the list of accepted answers by a human being, apart from some things that are accepted automatically as synonyms (you accept 'mom', then 'mother' and 'mum' get accepted automatically) or contractions (do not -> don't). As you know, the automatic contraction acceptance can lead to accepting/suggesting things that are completely wrong :/ But "cos" will not be accepted unless I (mistakenly) put it myself, although it will be 'accepted with a typo' because the system treats lack of special characters this way.
The reports are grouped without taking into consideration special characters, unfortunately. So if there's literally one report for "wez cos innego", I see it in yellow, and I will reject (remove) it, as technically it's not a correct answer. But if there are two reports, one for "wezcie cos innego" and one for "Weźcie coś innego", they will be put together. After I add "Weźcie coś innego" to the list, those two reports that are put together will turn green. Then I click an 'accept' button, which sends notifications to people that reported the newly accepted answers. And well, unfortunately the person who reported "wezcie cos innego" will also get such a notification, although their answer wasn't technically correct.