I am communication engineer with MSc in wireless networks , with 15 years experience in Aviation IT , PMP , ITIL certified , 80% of my work related to networks , ICT. i used information security in my work but not full time. i studied authorized book of ISC of mike chapple very well covering 8 domains , i answered more than 1800 Questions , 1 month dedicated studying before exam. but after all of this i failed , during the exam i found many many of questions i didnt understand what they are asking for ? i didnt understand the concept , i never saw may questions before. i need your advise what is my mistake ? how i can pass this exam ? do i need book camp or another materials or more questions from where ?