Is paying sums of money to a responsible employee after the completion of projects, which he requests in exchange for his help in obtaining these projects, considered a bribe? What is the ruling on this transaction? And is it necessary to stop working in the contracting field if these are the prevailing conditions?

It is not permissible for an official to receive a financial reward or to stipulate his participation with contractors in exchange for helping them obtain a project; because that is considered a bribe, which is forbidden to give or accept, due to the betrayal of trust and injustice to others involved therein. However, if you are more deserving of these projects and found no way to obtain them except by paying a bribe, then there is no sin in that, and the sin is on the receiver, not the giver. You are not required to stop your contracting profession, but you are required to stop paying bribes where it is not permissible for you to give them.