Translation:We need to slice mushrooms for the salad.
English has bee my native language for over 40 years now. It would be perfectly normal to say " we need to slice mushrooms for salad." This would be used if you are not referring to any particular salad. The sentence is desiginating the mushrooms specifically for salad and no other uses.
The Russian course takes me about 10 times as long as Spanish, Italian, and French, because I'm constantly referring to all sorts of tables to make sure I get the right form of pronouns, the right case endings, the right case after pronouns, etc. It's just not easy at all. The course definitely could be better designed to be more user-friendly, but still, the language is a real bear and extremely challenging, no question about that.
I verify everything in painstaking, slow-motion. It's beyond tedious. Other on-line courses are no better, and some are even worse. Not to mention the fact that, based on listening to native speakers say words at forvo.com, the computer voice is highly inaccurate.
You make good points but then eventually we just have to face that for English speakers it's simply a lot harder to learn Russian than Spanish, Italian or French. No matter how good the course is it'll still be vastly more difficult, especially when you start up and you have to familiarize yourself with the alien grammar and completely different vocabulary.
That's not to say that I think the duolingo course is flawless, in particular I think the "tips and notes" at the beginning of the lessons is often way too superficial to really stand on its own while still managing to sneak tricky usage note that are frankly way beyond the skill level of the lesson. I really recommend to anybody following this course to use a third party grammar book, "The New Penguin Russian Course" is often recommended and I can vouch for it, it's a great in-depth introduction to Russian grammar.
I loved that course through lesson 7. It was super helpful with explaining grammar, but my brain got kn overload and i also wanted more examples. That russian course is very compztible with duo. Also, learn russian in your car was fantastic if you drive a lot.
As an old dog, i hope to speal fluent Russian be time I'm 150 years old.
Dont worry. Russians tell me they must take 10 years of Russian grammar, and they dont remember any of it! I like Duo because after a while, a lot starts to sound right. Grammar books give tables difficult to remember and very few examples. So here you learn the natural way, except this is easy for kids, not so much for adults. So we get this section, and helps with explanations.
From what I've learned so far, I disagree with mtadych's explanation. "dessert" here is an activity, meaning "to eat dessert", like "for lunch" uses на because обед is a process or activity or eating lunch. When you have something which merely becomes part of something else, like mushrooms for a salad, there is no process of eating the salad when you say "for the salad", so you use для.
Also, дла seems to be a much more generic kind of "for", while на, when it doesn't involve static location, has some specific idiomatic usages - as in "for breakfast, for lunch, for dinner, for dessert" and others. That's just a general impression I've formed so far.
Except that на обед = "for lunch" is not about location, it's about the activity of eating lunch. На has a lot of different uses, if you look in Kaplan's English-Russian dictionary.
I think it''s a bit misleading to say that the mushrooms are "for the purpose of the salad" - the salad doesn't have any purpose, at least not in the sense that lunch or dinner has. The salad is just a thing, and the mushrooms are intended to become part of that thing, so they are "for the salad" - they are to become part of the stationary salad.
You cut the mushroom "for the purpose of the salad", that makes complete sense to me. The cutting of the mushroom does have a purpose, which is to make the salad.
You're right that на can mean a bunch of things, including "for" in some contexts. For instance I encountered "столик на двоих" meaning "a table for two" in the memrise course.
"Chopping" is a very different kind of kitchen procedure from "slicing". You end up with a very different end-product when you chop mushrooms than when you slice them. Chopped mushrooms are in small little bits, while sliced mushrooms are in bigger cross-sections of the entire mushroom.
Here's four recordings of the word by native speakers, all accenting the first syllable: https://forvo.com/word/%D0%B3%D1%80%D0%B8%D0%B1%D1%8B/#ru
My conjugation table gives two nearly identical forms for Imperfective/Perfective versions of infinitive: нареза́ть / наре́зать.
The accent marks over the á in Imperfective and é in Perfective are there only as a pronunciation guide in the table, and don't appear (I don't believe) in regular texts.
This should prove to be quite challenging even to a native speaking reading these texts, I'd think. But maybe not - perhaps there is some sort of context which enables the distinction, though it seems like a chicken-and-egg kind of issue.