I am not a Jew but I only left christianity not too long ago, I find the Jewish belief on heaven and hell fascinating
Some say it’s forever while others like Rabbi Akiva, The Rambam, Modern Chabad, the Ramchal say gehinnom is not forever and the worst punishment is annihilation.
Anyway I’d like to know what the Tanya says on the subject if anyone can be of help.
Tanya Likutei Amarim ch. 8 writes (translation Chabad)
But with regard to forbidden speech, such as scoffing and slander and the like, which being prohibited stem from the three completely unclean kelipot, the “Hollow of a Sling” (alone) does not suffice to cleanse and remove the impurity of the soul, but it (the soul) must descend into Gehinom (Purgatory—which is a greater punishment and thus more effective in cleansing the soul).
So, too, with one who is able to engage in the study of Torah but occupies himself instead with idle chatter — the “Hollow of the Sling” alone cannot effectively scour and cleanse his soul, but it must receive the severe penalties which are meted out for neglect of the Torah in particular apart from the general retribution for the neglect of positive commandments through indolence, namely the “Purgatory of Snow,” as is explained elsewhere.
And Chabad comments
The purgatory (Gehinom), where the soul is cleansed of the “stains” of sin so that it may enter Paradise to enjoy the radiance of G‑d’s glory, operates on the principle of “measure for measure,” i.e., punishment in kind. Thus, sins of commission caused by the heat of passion and lust are cleansed in a “Gehinom (nehar, lit., “stream”) of Fire,” while sins of omission, due to indolence and coolness (i.e., lack of fervor), are cleansed in a “Gehinom of Snow.”