You can check out the details of the exam here.
eg To be certified as Mendix Intermediate Developer, you must successfully complete the Intermediate Developer Certification Exam. The exam consists of 50 multiple-choice questions based on theory and practical scenarios. You have 90 minutes to complete the exam, and the passing grade is 75%
I would recommend that next to the intermediate learning paths (minimum you should do is the list that is on the certification page I shared above), you should have at least 6 weeks hands on experience, because that way the information will stick.
As a refresher before taking the exam, you could sign up for an intermediate developer course with one of the training partners.