Is it obligatory to abstain from working in the contracting field due to forbidden practices (such as bribery and deficiencies in specifications), and how does one repent for unlawfully acquired money from the past, and is prayer presented before repentance or vice versa?

Bribery to obtain a right or ward off harm is not forbidden for one who is compelled, and what is paid with this intention is not sinful. As for negligence at work and fraud, these involve injustice and infringement upon the rights of people. Repentance for this involves returning the right to its owner or seeking their forgiveness. If that is not possible, then by giving charity on their behalf, or by increasing good deeds and supplications. If the work can only be done by diminishing the rights of people, it must be abandoned. Prayer does not conflict with repentance from other sins, and abandoning prayer is one of the greatest sins after polytheism.