Am I obligated to repair the phone whose screen was accidentally broken at work, knowing that the repair cost (150 dinars) is close to the value of my wages (185 dinars), and I have already left the job?

A special employee is one whose benefit is measured by time, and they are entrusted with what is under their hand. A special employee does not guarantee what is damaged under their hand unless there is negligence or transgression, because what is under their hand is a trust, and oversight and error, which no human is free from, are not considered transgression. So, if the mobile phone fell without any transgression or negligence on your part, you are not liable for compensation.