Is giving money to a merchant to complete guaranteed government deals, with a percentage of the profits being received when the benefits of the deal return, considered usury, knowing that there is no contract proving the absence of loss and that the matter is based on trust?

If the money is a loan, then nothing extra should be taken on it, because "every loan that draws a benefit is usury."

However, if it is a Mudarabah (profit-sharing partnership), it is permissible, provided that the Mudarib (working partner) does not guarantee the capital, and that the benefit for the owner of the money is a known share of the profit, not of the capital.

The described form of transaction is invalid because the questioner takes a known percentage of the money (capital) and not from the profit.

To correct it, an agreement must be made with the Mudarib for a known percentage of the profit if it occurs. Any loss would be from the capital, and the Mudarib would lose only his effort.