Visitor Visa - B2

Please Sir/ma I need your assistance, i went for my interview yesterday and my visa was refused, i applied for b1/b2. Am a Firefighter from Nigeria, 34yrs old, married with a kid, my monthly salary is around $752, i want to visit my instructor(citizen) to learn more about my job for 2 weeks during my annual leave which will commence by early March this year,i have all the documents with invitation letter to back my case but the Consular Officer did not even ask for any document, just two questions. The interview goes this way:

1,VO: Good morning
  me: Good morning sir
2,VO: Why do you want to go to US?
  me: I want to visit my instructor Mr.xxxx xxxx
3,VO: How much is your monthly income?
  me: #150,568 ($752)

  VO: its not what you can go U.S for, sorry your visa is not approved this time, and gave me one blue card which is 214(b) when i go through the card it was stated that i can reapply any time but some information must change from the old Application form.

Please Sir/Ma, am thinking of reapply, my question is that, what category visa can i choose? because i want to go and learn more about my job for just two weeks, not from a University or College but from a Fire Service Department in U.S. and they have arrange for my visit over there. I wanted to tell Visa Officer that i want to go and learn more about my job for two weeks, but someone told me that, learning visa is different from visiting visa, and visiting visa was the one i applied. Pls assist me with your experience, i would appreciate your quick response. Thanks.