"Do not do this, you have a more important problem now."
Translation:Nie rób tego, masz teraz ważniejszy problem.
I know this is 2 years old, but Vengir, this is really a great description of perfective. This is interesting. So it really feels like something you will finish, or have finished, when using perspective. It is the emphasis of it that makes them so different to natives, I hope I am right in this. If you say rób, it really means only doing, no matter when it is finished or if at all. It is also more about the general concept. So it is not like in my native language, German, where there is no such concept, no difference in doing something vs being definitely finishing it (strange description, but it seems fitting, to me at least). You either do it or you don't. I wonder if there is a perfective aspect to every verb? What are the exceptions?
Off the top of my head, I found only one likely exception: mieć. (there might be more of course, but I can't remember) The closest thing in my opinion that would count as a perfective version of "mieć" would "otrzymać", but that's a stretch.
Besides that one a lot depends on what you count as the perfective version. The verb "widzieć" does have the perfective "zobaczyć", even though they don't share the core. "Umieć" doesn't seem to have one in standard Polish, but the youth slang has "naumieć się/wyumieć się" (which is really equivalent to "nauczyć się").
And then you have verbs that can only change their meaning completely when they get a perfective prefix, like "móc" becoming "pomóc"; I can see some relationship, but I wouldn't think of them as equivalent, specially since "pomóc" has its own imperfective equivalent: "pomagać".
That use of progressive in a negative imperative ("Don't you be doing that!") was once mentioned to me as a partial parallel that might help English speakers remember to use imperfective forms in negative imperatives in Russian. It is something I vaguely recognize as slightly old-fashioned informal speech, but it is not something I would say or write.
There surely are some collocations, and I think "kłopot" is often more serious. For example is someone was in danger, saying that he or she "ma problem(y)" would seem like a big understatement, that should rather be "kłopoty" in plural.
We don't speak about "problems" in maths - unless I misunderstand something, that's simply "zadanie" (task) or "ćwiczenie" (exercise). We also say "przykład" (example). For example in my "zeszyt ćwiczeń" (exercise book?) Zadanie 1 can have 10 "przykłady" - 10 equations to solve.