What is the correct way to use Precedence bulk, junk or list, list-unsubscribe, etc.?

Question

Email Marketing

Tell me, please, who faced with the mass mailing of letters. What are headers for? Using Precedence bulk, junk or list, list-unsubscribe, etc. and how to use them correctly?
Actually, I have a small database of e-mail addresses, I bought software, started mailing, and a lot of letters went to spam. I found out that due to the lack of SPF in the first place, I fixed it.
Along the way, I came across information about the headers in the letters. I would like to understand how to set these headers correctly.
Postal services recommend using them when sending mailing lists. But nowhere did he find what he was responsible for, he turned to the toster.ru community.

Answer 1

The best description I've seen in English is from MailChimp .
Mail.ru also publishes recommendations for newsletter authors.

Answer 2

I read recommendations on mailings from Yandex and mail, but something doesn’t really help.
Maybe I'm already under sanctions?
How to check it!?