Should I inform the administration that the consultant tried to bribe a government employee, knowing that the administration is foreign and does not care about what is lawful or unlawful? And would I be sinful if I do not? And is it considered unlawful for me to accept a sum of money from the consultant in exchange for helping the administration accept the bribe, and must I inform the administration about this sum?

Bribery is forbidden and is fundamentally a major sin. The Prophet, peace and blessings be upon him, cursed both the briber and the bribed. It is only permissible if the payer is compelled to it to ward off injustice or reclaim a right. It is not permissible to assist in it if it is forbidden; rather, one must forbid it and inform the company management if the consultant does not desist. However, if it is permissible, there is no issue in paying it or assisting in it, but it is not permissible to accept money without the company's permission.