Sure, @ncagutierrezart! I like trying to answer questions. 🙂
Yes, the English word heresy does come from Gr. hairesis, via Old French and Latin (where it means “school of thought” or “philosophical sect”). Here’s some more information from one of my favorite websites, the Online Etymology Dictionary: heresy (n.).
The word hairesis ultimately comes from Gr. αἱρέω (a common verb with the primary meaning “take” and a bunch of secondary meanings). The form αἱρέομαι is in the middle voice (αἱρέω is in the active voice) and means “take to oneself” or, by extension, “choose.”
If you’d like to look up more detailed information about the verb αἱρέω (or other Greek words), I’d recommend the University of Chicago’s Logeion app, which draws from major classical dictionaries and includes examples from the ancient corpus, or Tuft’s Perseus Digital Library (a lifesaver for me in college!).
I don’t know what kind of computer you have, but if you’re interesting in learning how to type in the Greek alphabet, try googling how to type in Ancient Greek (polytonic). There’s a lot of good resources out there from various classics departments. The keyboard used is called polytonic Greek, which I’ve installed on my devices in addition to the regular English keyboard.