Is the "Qareen" real, and to what extent does it influence a person, and is it permissible for us to believe in its existence?

The existence of the Qareen (companion) is affirmed in the Quran and Sunnah. In the Noble Quran, Allah Almighty says: (His companion [satan] will say, "Our Lord, I did not make him transgress, but he [himself] was in extreme error.") [Quran, 50:27]. The Qareen referred to here is Satan. In the Prophetic Sunnah, Aisha (may Allah be pleased with her) narrated that the Prophet (peace be upon him) said that every human being has a devil with him, even himself, but Allah helped him against it until it submitted. A Muslim must believe in its existence because it is among the things reported by the Quran and Sunnah.