Is the salary received by the questioner considered unlawful, taking into account that a portion of their time at work is wasted on personal matters, and what should they do to feel at ease about this, especially after losing $8,000 due to being preoccupied with personal matters?

If you are a private employee in an institution, it is obligatory for you to adhere to work throughout the period specified in the contract. It is not permissible for you to exploit work time for personal matters except with the permission of the officials. Therefore, you must repent for what you have done and resolve not to return to it. Your repentance is not complete except by seeking permission from the officials. If that is difficult for fear of harm, then you must estimate the value of the time you exploited for your own benefit and return it to the institution without requiring their knowledge or consent.