Is it permissible to take a sum of money in exchange for helping someone sell devices to the government, and what should be done with the amounts that have been taken?

The person who buys devices from you as an agent for a government entity—your giving him a gift is considered prohibited bribery. You must repent to Allah, resolve not to return to this sin, and try to recover the money you paid him and deliver it to the company by any possible means to clear your conscience.