Obviously the ISIL and the Al-Queda know your religion better than you do. They read the Quran and they kill.
What you believe has no existential value at all. You have been exposed to the Quran since childhood and you believe what it makes you believe. There are readers of Quran who employ reason and reject it.
Making you believe is the purpose of the Quran. Anyone can make you believe, whatever the relation of that belief to truth. Watch from minute 10.15 to 10.45:
Sadhguru - 2017 prophecy! Nobody can believe this!