What is the ruling on taking a plot of land granted by the municipality, knowing that a municipal employee registered my name for it in exchange for half the value of the land, and is what the employee is demanding considered a bribe?

If the employee is responsible for granting land, then what he takes is a forbidden bribe. If he is not responsible, then there is no harm in what he takes in return for effort and work, not merely for intercession. However, if it is highly probable that he is paying a bribe, then it is not permissible to seek his help. What this person is doing falls under the category of forbidden bribery. If the transaction was a forbidden bribe, then one must repent to Allah, and there is no harm in benefiting from the land if the conditions for its grant apply to you. It is not permissible to give this person half the value of the land if it was a bribe, because spending it is forbidden.