"Positives" or "negatives" aren't necessarily incorrect, but neither are they the proper way to say what is meant. They're the sort of words that comes from business meetings where managers want to make their point sound important, but dumb it down into meaningless (or invented) words and phrases. Words like "excellence", "integrate", "synergy", "teamwork", etc etc have all had their original meanings thrown out the window by well-meaning businessmen with limited vocabularies.

Anyway, back to your question. Instead of "positives" or "negatives", it would be better to say "pros" and "cons", as these nouns have been around for a bit longer (though they've probably also achieved prominence through overuse at business meetings).

Also, I don't think the terms have been borrowed from German specifically. I think it's just lazy English.

I disagree about the "dumbing down" (and yes... I have used it :))
It may have started out as lazy and incorrect, but it is common business usage (at all levels). Yes, it does refer to positive/negative aspects, points, etc.
pros and cons is OK as well, but not quite the same in nuance IMHO = points for and against
positives and negatives = positive points/negative points

Some adjectives (and other parts of speech) can be nouned.

A non-native has to be careful because you can't do this with all adjectives, but, in appropriate contexts, it is a fairly normal way of referring to anything that can be listed under the heading "Positive" without the unwanted, and possibly inaccurate, precision of adding a noun like "aspect" (unless "aspect" is intended to have no semantic content).

. . . IMHO, of course.