Teshuvah for Noachides
Hi, I have some questions regarding teshuvah for Jews and Noahides. As I understand teshuvah, there is two levels. The first level turns the intentional sin into an unintentional sin. That lowers the punishment, but it does not remove the sin. The second level removes the sin, and you are no longer guilty in the eyes of G-d.
I recently heard from a rabbi, that it does not work like that for Noahides. We (Noahides) do not have a way to remove a sin completely. We can do teshuvah, but the sin will not be completely removed. Just as the first level of teshuvah for Jews. Therefore there is no way for a Noahide to be completely forgiven, which means that he/she will still be punished.
The only way around this, is to convert to Judaism and to get a new soul that “starts at zero,” you can say. Considering that most Noahides are former Christians and that idolatry is a serious sin, it sounds like converting is the only right thing to do. In general people make mistakes that they regret later, if they are former Christians or not.
Is this view of teshuvah true? If yes, what is the sources for it? And why do Jews then discourage Noahides of converting, if it is the only way to be completely forgiven?