Is it permissible to benefit from the financial amounts paid under the name of "overtime and night shifts" in a government job, knowing that no actual overtime is performed and the actual night work is much less than what is calculated?

It is not permissible for a government employee to take money for hours of work not performed, as this is a lie and an unlawful appropriation of public funds. One must refrain from taking such money until it is verified that it is disbursed in a permissible manner, free from falsehood or fraud against public funds.