Here is a funny and instructive blog-post in TheEconomist about some of the things Brazilians say and can confuse Gringos:
What Brazilians say: I'm nearly there (Tô chegando)
What foreigners hear: He's nearly here
What Brazilians mean: I've set out
What Brazilians say: I'll be there in ten minutes (Vou chegar em dez minutinhos)
What foreigners hear: He'll be here soon
What Brazilians mean: Some time in the next half-hour I'll get up off the sofa and start looking for my car keys
What Brazilians say: I'll show up later (Vou aparecer mais tarde)
What foreigners hear: He'll be here later
What Brazilians mean: I won't be coming
What Brazilians say: Let's stay in touch, ok? (A gente se vê, vamos combinar, ta?)
What foreigners hear: He'd like to stay in touch (though, puzzlingly, we don't seem to have swapped contact details)
What Brazilians mean: No more than a Briton means by: "Nice weather, isn't it?"
What Brazilians say: I'm going to tell you something/ Let me tell you something/ It's the following/ Just look and you'll see (Vou te falar uma coisa/ Deixa te falar uma coisa/ É o seguinte/ Olha só pra você ver)
What foreigners hear (especially after many repetitions): He thinks I'm totally inattentive or perhaps mentally deficient
What Brazilians mean: Ahem (it's just a verbal throat-clear)
What Brazilians say: You speak Portuguese really, really well! (Você fala português super-bem!)
What foreigners hear: How great! My grammar and accent must be coming on a lot better than I thought
What Brazilians mean: How great! A foreigner is trying to learn Portuguese! Admittedly, the grammar and accent are so awful I can barely understand a word... but anyway! A foreigner is trying to learn Portuguese!
There is more of that in the blog post.