Tae Kim’s Guide to Japanese Grammar

I have been studying for around a month and a half now, and I have mixed feelings on the book. I started going through it after going through some JFZ1 and it is a bit confusing. I understand that he focuses on the casual spoken Japanese, but he skips through some vital stuff like the polite form of verbs (which i got so confused by I had to refer back to JFZ1, as I was seeing the polite form everywhere I tried reading). I want to carry on using the book but I want to also understand polite speech as I plan to live and work in Japan when I graduate from university and knowing polite forms will be necessary when working. I like the order that Tae Kim is going through things but I would also like to know good supplementary guides to understanding the stuff a bit better and understanding the polite forms as well.

I have also got myself a bit muddled up by going between Tae Kim and JFZ1. I think I am probably just overthinking the language though. Some help would be really appreciated