Talking about the Exam Syllabus they are generally 4 weeks long be it online or offline. With these, you get proper guidance from an expert along with various study materials. For the Project Management Certifications exam, I would say, the more the merrier. Not only this, going through the training will help you in gaining a stronghold on Project management fundamentals.
Also, you can enhance your speed and boost your confidence by taking up various full mock exams. These 6-8 weeks will be a crucial part of your preparation as this is the time where you have put your mind and soul into the preparation.
You may also go through this recording https://youtu.be/rnUcFwXeibk of PMP® Exam Prep where you can understand the topics in a detailed manner with examples.
The only mantra to clear your PMP® certification exam is to learn the entire PMBOK® Guide by heart. For more details, I would suggest you visit here: https://www.edureka.co/blog/pmp-exam-all-you-need-to-know/#pmpsyllabus