slang words? umm.. we actually have plenty of 'em x)
kok, duh, ah, oh, sih, eh are most common slang words we use in daily life.
lo = kamu. (it's refering from Betawi dialect)
gue = saya. (also refers from Betawi)
for daily conversations, we don't really necessary to use formal sentences.
e.g: Why are you so long? =
Formal: Kenapa kamu lama sekali?
Not formal/slang: 1. lama banget sih? (overreacted) 2. kenapa lama banget sih lo? (too emotional)
it takes ages to explain all of them :) slowly you can learn slang words, but it doesnt necessary.