In regards to becoming a firefighter here is an excellent article: https://www.firescience.org/how-to-become-a-firefighter/
Each fire district is different.
Some fire districts want you to become an EMT BEFORE you become affiliated with them.
Some want you they want you to go to fire academy first before EMT courses.
Contact fire districts’ volunteer departments and speak about your goals. One will be the right fit for you.