"We need to cook shchi for lunch."
Translation:Нам надо приготовить щи на обед.
Ah, ok... I didn't know the perfective /imperfective distinction. I'll need to study the "aspect" concept.
Yeah, getting comfortable with aspect is essential. I like the summary here: http://preview.tinyurl.com/mbxeyxa ...or to have someone walk you through it, google "Russian verbs aspect" and choose video - there are several explanations on youtube (including mine on the Russian grammar channel).
I'm not a native Russian speaker so someone else please correct me if I'm wrong. But to try to answer your question:
Not exactly, but there are ways of communicating it with extra words. It's not built into the verb forms the way it is in Russian. In English, when we want to communicate these things, we do so by using "helper" words.
For example in English, in past tense, we use constructions like "I used to do that." to communicate repeated or habitual actions that are covered by imperfective verbs. Romance languages use the "imperfect" past tense to communicate this. In English, we use constructions like "I have done that." to communicate simple, completed actions, like the perfective in Russian, for past tense.
In future, we often use constructions like: "I will be doing that." to communicate imperfective, although in English, saying "I will do that." is a bit more ambiguous, corresponding to either future perfective or imperfective verbs in Russian.
Kind of like in German and some other languages, Russian dosen't distinguish in present tense between constructions like "I read" and "I am reading". In Russian, you can only use imperfective forms in the present, and they encompass both of these meanings.
Basically, the deep answer is...as with comparing any languages, each language makes a different set of distinctions, and there are usually some ways of communicating similar things, but they don't correspond in a 1-to-1 way.
Absolutely. English has what are called the simple and the perfect aspect, in addition to two others (not relevant).
In english, the standard construction of perfect verbs is combining a past participle (typically ends in -ed) and the verb 'have' fully conjugated.
Simple: I cook shchi. Perfect: I have cooked some shchi. (A determiner needs to be there in order to clear up ambiguity.)
Готовить (with the soft sign!) is imperfective, which is used for repeated actions, or an action in progress, or when the idea of completion & result isn't important. Приготовить (perfective) is typically used for a one-time action that has been (or will be) completed, with a result. The choice of aspect is very sensitive to context, and Duolingo unfortunately doesn't provide much context. I suspect they prefer perfective (приготовить) here assuming that the щи needs to be ready for lunch – there's a result that's relevant.
So far, this is what Duo has taught me regarding "for":
«Тарелка для риса, а тарелка на обед»
"A plate for rice, and a plate for lunch"
The dictionary entry for на is really long, with a large number of different translations and uses, some very particular to certain idioms. The dictionary entry for для is much shorter. The import I take from that is that для is the usual "for", while на depends on idiomatic factors which have to be memorized, although there are certain general rules about на that help narrow down this issue: at least, на is used in prepositional case for stationary (not moving) location of things, на столе = "on the table" and in accusative case for processes like engaging in a meal; the accusative на is also used for location where movement is involved - a process-oriented kind of situation. But if I had to guess, I'd probably use для for "for" if I didn't know the correct word.
We usually use "приготовить" because our aim is not in cooking, not in the process of cutting vegetables, but in the having the meal or dish done. You say "мне нужно готовить обед" if you want to specify that you need to be busy now with the process, it might be said in the situation when you letting your friend know why you need to leave. As a different example: "i need to prepare for the exams" - "Мне надо готовиться к экзаменам" you are emphathizing, that you will take time preparing for them, may be these exams are in 2 months only, so your process of preparing pretty much not gonna be done this time or today. "Мне надо приготовиться к экзаменам" will be understood as your exams are may be tomorrow already and you have only this evening to cover all the studing materials, so you're planning to be done with preparing today or this time.
На is used with prepositional/locative when it expresses position ('on' or 'at'), but it can be used with accusative for other contexts. "For dinner/breakfast/lunch/dessert" etc = на + accusative. It's always a good idea to watch the context carefully - some other prepositions can also be used with different cases, depending on the meaning & context.