English: textbook vs. reality
What a textbook chapter on English gets right, what it skips, and the slang, ellipsis, and tone shifts native speakers actually use day to day.
English textbooks generally do a decent job with the basics, but they tend to over-rely on one register — clean, polite, complete sentences. Real spoken English has a wider range: contractions are standard (not optional), responses are shorter than textbook dialogues suggest, and some very common phrases are introduced late or not at all.
Greetings
"Hello" is perfectly fine — the textbook gets this right. What textbooks often miss is "Hi," which is the most common everyday greeting in English and works in almost any situation. They also rarely explain that "What's up?" is not actually a question — it's a greeting that expects a brief response, not a detailed answer.