I think that it depends on your personal situation. If you want to complete your personal training course and get the certification you need to spend a lot of time on that. Some people using do my assignment services like https://au.papersowl.com/do-my-assignment or any other service like this one. You need to pass exams and show your experience on this subject. Fitness exams are not that simple but I think that everyone who uses assignment services could do that. At least I think so. I would recommend you to watch some videos on YouTube and read more on this forum. This would give you enough information about the training course. And don’t forget that your study depends on the certification you are studying for. This is an important thing.
It is dependent on the person’s background and knowledge. Years ago I took a number cert exams just to experience them for my programs that teach Personal Training to hopeful instructors. I passed them without extra studying, but I already had the background.
I wouldn’t want an instructor to just manage to take the exam though. There is so much more to being a fitness instructor.
…and then I should add, even if you already have a certification, it still takes a good amount of time to study for a second PT certification. The way they program design can be totally different. Although the physiology doesn’t change, sometimes the acronyms change; for example, one certification used “frequency, intensity, time, type” and another one used “frequency, intensity, duration, mode” for variables that one could change in an exercise program.