Office job help please?

• medical office assistant
• knowledge base software
• medical assistant job duties

Hey I really want to work in office I been looking into legal assistant job, business administration and marketing. I'm completely starting of from the bottom I am taking a course in math and English to gain my GCSE I really like the idea to get struck in do hard-work Which is the best out of these and how long do you have to train

I appreciate your advice.

Office job help please?