Doing one’s own work during official work hours

If the
second job requires leaving the workplace of the first job, then it is clear
that this is not permitted, because it is breaking the conditions of the
first job. The first job stipulates that he should stay there until this
hour until this hour, and the Muslims are bound by their conditions. If the
other job does not require him to leave the first workplace and will not
conflict with it or delay it, and he is only doing something when he finds
free time during his work, it seems that this does not do any harm, because
so long as he is not busy during this time, then the time is wasted and not
put to good use.