Hi, is "il est Professeur" / "Elle est Professeur" correct (no article before profession).

Yes, it's correct: see Don't use un, une when giving people's professions (zero article)

Lisa est une très bonne vendeuse. In French, you always need an article in front of a group including an adjective, and that rule applies to professions: Paul est un professeur extraordinaire. Otherwise: Paul est professeur. (note: no adjective, hence no article)