Is it permissible to give a university professor a calculator as a bribe to avoid his harm to a student's grades, knowing that he does not fear God and his side is not secure?

If there is no reason for a gift to the teacher, then what is presented to him is considered a bribe, especially if it is at his request. The bribe that is forbidden to pay is that which is used to establish falsehood or abolish truth. It is forbidden for both the giver and the receiver, as the Prophet, peace and blessings be upon him, said: "The Messenger of Allah, peace and blessings be upon him, cursed the briber and the bribed."

However, if the bribe is to remove injustice or attain a right, then it is forbidden for the receiver but not for the giver. So, if it is highly probable that the teacher will wrong you or withhold your right, it is permissible for you to pay what he demanded. It has been narrated from Ibn Mas'ud and a group of Tabi'in that it is permissible to pay money to دفع الظلم عن النفس والمال.