Is it permissible for an employee working in customs clearance to take a small amount of money from clients in exchange for facilitating paper transactions, with the employer's consent?

The preponderant opinion is that if a Muslim is in a country where they only know of long fasting, there is no harm in them fasting with the people there, as long as it does not harm them. However, if they know of a shorter fast in that country, they must observe the shorter fast, because Allah the Almighty desires ease for His servants, not hardship. Exaggeration in worship is disliked, for the Prophet, peace and blessings be upon him, said: "Indeed, this religion is easy, and no one will ever overpower it. So, be straight and moderate, and rejoice." It is also narrated: "The most beloved religion to Allah is the tolerant, easygoing monotheism (al-Hanafiyyah al-Samhah)." If this long fast harms them or leads to their demise, then it is not permissible for them, due to Allah the Almighty’s saying: "And do not throw yourselves with your own hands into destruction" [Al-Baqarah: 195]. And they should ask the people of knowledge in those lands about fasting.