Also, Tae Kim's Guide to Learning Japanese is helpful... ^.^ http://www.guidetojapanese.org/learn/grammar But, you could also read some light novels and manga. Keep in mind, though, that you might need books with furigana, if you don't know very many kanji.

Hi there, Japanese grammar is pure logic and uses something called "scramble", which means you can put everything in the order you like to. Nevertheless, the only restriction is that the main verb must be on the end of the sentence. I advice you to start learning the basics, once you have mastered that you will start constructing complex frases really fast.

in my opinion, long sentences show up mostly in written text, rather than oral expressions. if your japanese is good enough, try to read some materials other than simple textbooks. eg. newspapers (also available online: yomiuri, asahi), novels(expecially those have both japanese version and translations in you own language).