In most countries there is a distinct difference between formal and informal language. In English there is a difference, but it's not as clear nor is it always observed.
For instance in corporate America I would probably not greet my potential boss (at the interview, for example) with a simple, curt, "How's it going?"
However, I might say, "How's it going, Bill? It's good to meet you." This would be considered warm, yet respectful. In fact, if I were taking a new job at this time, I would feel that this might be the most welcome greeting to someone who works all day in corporate America.
Another thing that many people learn while learning English in foreign countries is that contractions (the practice of shortening words and putting them together (or concatenating)) are not for use in business communications. To that I can only say, "au contraire!!"
I worked for ten years in consulting around and in NYC with firms such as Goldman Sachs, GE Capital, IBM, AT&T, and more. In fact, my job at several firms was to offer advice to people who were considered poor communicators, or who were "habitually" poorly understood. I must say that everyone...and I mean EVERYONE used contractions. Not using contractions can actually change the tone of writing.
For instance, saying "I did not" instead of "I didn't" makes the writer seem as if they are slightly emphasizing "did not". The reader then thinks, "why is he emphasizing those two words?" No matter how briefly, any distractions from the tone or message of a communication can doom it.
To be more clear on this point, consider that often I would go for one-on-one's in my client's office. At the beginning of which I'd say "How's it going?"
The answer was usually something about the astronomical amount (that means "extremely high number of") unread emails in his inbox. The numbers were incredible...20, 50, 70...try 700!!!
Therefore, the last thing you want to do is to create moments of confusion. Be respectful of the number of emails people have to read. The less thinking about extraneous matters that they have to do, the better.
So, if you want to sound more like a native speaker, learn contractions and use them. They add a level of warmth to your communications, and that is probably a good thing in most cases.