No, I mean that there are at least a half a dozen different ways to express "if", and they all have specific semantic uses. It is way, way more complicated than syntax.
I've been studying Japanese for years and I am at a basic intermediate level. I still find grammar hard to read, and even harder to produce naturally. I may just be particularly thick but I think saying "you can master Japanese grammar in a matter of weeks" is pretty misleading.
[0] http://www.learn-japanese-adventure.com/japanese-conditional...
Japanese grammar is simpler than English in some ways, harder in others. Overall though, it's really, really hard.
1. by which I mean, in the case of English, for example, if your native language is not french, german, etc.
In fact, I think English is harder to learn for Japanese native speakers than Japanese for English native speakers.
But as a general principle, I believe that learning any new language is really, really hard. The people who claim to master languages in a few weeks are usually full of it (and by "usually", I mean "essentially always".)