If I take Progesterone as a man, what are the effects? I read it reduces testosterone levels? Is it sufficient for castration?

I would avoid doing that. Progesterone works very well in an HRT program. I have read on a doctors page where he said to avoid taking it by itself.

I am on hrt and take progesterone along with estrogen with out taking estrogen it doesnt do much you need higher levels of estrogen to have an effect from progesterone.

I think you are thinking of Progestin same class but synthetic Depo Provera which is a progestin has been used for chemical castration but I found it doesnt work as good as Androcur that worked with in about 2 weeks for me along with low dose estrogen. Now I'm on estrogen injections and my t count is 16ng and estrogen is around 300pg