How to prepare for Unity Proffesional/Expert Programmer exam?

Hello, I'm interested in getting certified as a unity developer. The standard exam however seems a little too easy (as I see it's intended for beginners, and I have a few years of experience). So I was looking at the Professional/Expert levels, but I don't dare sign up because I don't know what to expect.

I've had long chats with the staff but nothing was useful. I read everything on the exam page, I know they have some "objectives" and even a couple of sample questions, but I'm not willing to risk 200$ on something I have no idea if I'm prepared for or not.

For example, one of the "objectives" of the exam was "performance improvement". And that is as vague as it gets, I can imagine the most trivial questions or nearly impossible ones. How am I expected to sign up (and pay) for an exam where I have no clue what to expect? Sure it says it';s intended for developers with X years experience, but that is also really vague. In my experience I never worked with multiplayer, and I know that's also a topic, thus proving I can't rely on experience alone.

So my question is, are there any courses I can take that guarantee I'll be ready for the exam (provided I have all the knowledge in those courses), or some full exam samples I can look over so I know what to expect?