What are the best classes if you wanton join the fbi?

I'm not an expert, but you should definitely study law, criminology, some psychology, forensics, and some chemistry.

If you want to be a detective/officer, law, criminology, and psychology might be the best choice.

If you're into scientific analytical jobs, forensics and chemistry is probably the best.

Some more useful topics include physical science engineering, language proficiency, finance/accounting, and computer science.

And overall, you should probably have a healthy physical : P

First of all you must have a Bachelors in Criminal justice degree.

The job is only open for US citizens

You must study computer forensics, cyber crime, biology, criminal justice, and business administration.

You also get paid either 51,000 dollars a year or 70,000 dollars a year.

The Bachelors is a 4 year degree program and the Masters degree in Criminal Justice can be completed within 2 years. So, it may take around 6 years of education to become an FBI Agent.