It's probably best not to talk about downloading A Dictionary of Advanced Japanese Grammar from the internet, as the book is a paid resource and downloading it would constitute piracy.
I don't have the book on hand at the moment, but I'm familiar with it (and its companion volumes A Dictionary of Basic/Intermediate Japanese Grammar). They all contain highly detailed explanations of each grammar point covered, along with numerous example sentences. They don't just say "ni hikikae: in exchange for" and then leave the reader guessing without any clue of what exactly they mean. It boggles my mind how you could read the explanation and example sentences and still not have the slightest idea what they're talking about, or to be able to explain your confusion in any way other than "I just don't get it." (I know you're not a native English speaker, but this doesn't seem to be a problem with your English. From the tone of your posts, it sounds like you really haven't thought about or tried to understand the grammar for yourself at all.)
Also, your previous post was asking about some very fundamental points of Japanese. This particular grammatical structure (as one might suggest from the name of the book) is a rather advanced one (corresponding to JLPT N1 level, going by a quick internet search). It seems to me that there are far more basic elements of Japanese that you should be learning before worrying about obscure stuff like "ni hikikae". You mentioned before that you were thinking about taking a course. Are you doing so? Because a well-structured course would teach you the material in a more intuitive, organized fashion, so you wouldn't be worrying about stuff like "ni hikikae" before mastering far more basic, fundamental aspects of Japanese sentence structure.
I'm sorry that this isn't a simple answer to your question, but from the tone/content of your posts I can't help but feel like you're not learning Japanese in a particularly efficient or effective way. With no details of precisely what your confusion is, you're basically just asking us to type up an explanation of the grammar point, and there's no way we could give you something more comprehensive than what's in the book. (To put it another way, if you can't understand the explanations in A Dictionary of Advanced Japanese Grammar, you're probably not advanced enough to be using the book, and should probably be focusing elsewhere in your studies.)
(edited for clarity)