Is it permissible for my friend to repair his damaged laptop himself for 400 EGP instead of paying 1500 EGP to the company, knowing that there is a contract obliging him to pay a fixed amount in case of damage and preventing him from repairing it himself? And is the condition of compensation with a fixed amount permissible in Sharia?

The tools in the employee's possession are a trust (amanah (definition)), and the employee is not liable for them except in cases of transgression (ta'addi) or negligence (tafrit). The condition of absolute liability for the damage of a device is void because a private employee is a trustee and is not liable for what is damaged in their possession except through their transgression or negligence. If transgression or negligence is proven, the employee is liable for an equivalent item (mithli) if one exists, and if not, then for its value on the day of damage. Therefore, it is not permissible to stipulate a fixed amount for compensation regardless of the type of damage. If the damage occurred without transgression or negligence, then there is no liability on the employee. However, if it occurred due to transgression or negligence and the device can be repaired, then the employee is responsible for its repair.