Is a partner taking money from the the company without the knowledge of his partner considered theft, and is the money taken in this case considered unlawful, and what is the path to repentance if the amount cannot be determined?

The partner's disposal of company funds is based on agency. A partner is not permitted to dispose of joint funds except with the permission of their partner. If one partner takes money without the knowledge of the other and does not account for it, this is forbidden and reprehensible. The other partner is not allowed to respond to treachery with treachery. Rather, repentance is achieved by ceasing this act and accounting for what was taken from the profit or from the capital. If they are unsure of the amount, they should act based on their best judgment.