What happens to a goy when they die if I understand they don’t have a soul? And if idolatry brings a punsihment of "karet", then what happens to all the rest of the world that have so many idols like buda, krishna, and yeshu? And what’s the prurpose of every non Jewish person in the world if they don’t have soul? Are they valuable?

Gentiles definitely have a soul and go to heaven if they "keep the seven" (Noachid mitzvot)! The kabbala differentiates between the Jewish neshama and the non-Jewish soul, but both you and I are not kabbalists, so it's not that significant. I know for a fact that many Christians (including all of the Protestants, and many other denominations, even some of the Catholics) don't believe anymore that Yeshu was God, and I imagine that many rational Buddhists today also don't believe the ridiculous idea that a man or idol could be God. Accordingly, many, maybe even most, go to heaven. There is purpose and importance in every part of creation, and how much more so, in each and every person! The Jewish nation has a unique role to be a "Light for the Nations", but that davka shows that the gentile nations are super-important, as well! All the best!