A source for learning how to speak or write formaly?

Question

and thanks for helping me. I would like to know if there is a source so I can learn how to speak and write formally, mostly for these topics:\n\n-Sending a formal email to anyone or an organization or a professor\n\n-How to talk formally with a customer, your boss, or someone you find in the streets whom you only want to ask a question\n\n-How to write a formal article\n\n-What are formal phrases.\n\nThank you and feel free to tell me if I have written anything wrong in this post.

Answer 1

What you are referring to is "Business English." Use that as a search term and I'm sure you'll find more information than you need.

Answer 2

There are formal classes at the university that cover this subject, I think the title is "WRITING" and it is a prerequisite for students applying for graduate degree. I am pretty sure you can find books and tests as well.