What should I do about the money I am owed by some patients but did not receive from them before I suddenly left my job, and am I obligated to repay the money that some customers did not pay in my new job?

The employee is entrusted with their work and the employer's money, and is obligated to fulfill the conditions stipulated in the employment contract. If the pharmacy owner permits sales on credit, then there is no blame upon you, and you are not responsible for the loss of money. However, if the owner did not explicitly permit it, and you acted in this manner, then you have breached the trust. In this case, you are responsible for guaranteeing any money lost to the pharmacy owner, and you must inform them of those with whom you dealt. You are also obligated to repent and seek forgiveness for neglecting the trust.