ATPL ground training requires 650 hours of evidenced study time assuming you already have a PPL and are on the modular route, 750 hours otherwise. Assuming 35 hours a week that is a minimum of 18.5 weeks = 4.5 months solid study. In reality you will take time out to take exams or may do only 30 hours a week =5 to 6 months. Whoever told you it takes a minimum of three months was either wrong or assuming 50 hours study time a week, no breaks. I can't believe CATS have agreed that.