What are the major types of category of class ? And how long are the classes held for?

The training programs can be divided into six program categories: entry/junior level training, in-service training on policy and regulatory changes, in-service training involving confidentiality and specialization, in-service training for tax officials in local authorities, middle/senior-level managerial training, and international manpower and language training. And the duration of the courses is arranged by short-term, medium or long-term periods of time, from several days to 4 weeks.