There are some proper answers already, but I'd like to notice, that you're probably gonna use "положительный" most of the time instead of "позитивный" in spoken language. "Позитивный" is more about attitude, about mood, e.g. cheerful person can be called "позитивный/позитивная", and that's almost it. Also there are some special meanings of "позитивный" you can look up in a dictionary, but those are used rather rarely, IMHO. As for "негативный", it can be used to describe some grumpy or angry person or unkind attitude too, but it's also commonly used for unpleasant experience (thing is, that for pleasant experience native speaker would rather say "положительный опыт" than "позитивный опыт", IMHO). So again, in spoken language you're gonna mostly use "отрицательный". Hope that helps :)