Is it permissible to withdraw the difference in the amount from the company without the administration's knowledge, after the manager retracted the agreement to adjust the salary from dollars to euros, knowing that the value of the dollar has decreased, which led to a loss in salary?

The questioner's work at the company is a lease (ijara) that has specific legal rulings. Among these is that it is a binding contract for both parties, and neither party has the right to unilaterally terminate it except by mutual consent, or through the option of "taqabul" (reciprocal termination), or by stipulating a termination option (khiyar). This is based on the Almighty's saying: "O you who have believed, fulfill [your] contracts." So, if an employee and a company agree on a duration and a wage, the contract is binding until the duration expires, regardless of the dollar exchange rate. If the company owner dismisses him and they agree on a new wage, this new contract is binding for both the company and the employee. If the company owner does not fulfill the new contract and denies the worker's right, the worker may take his right without the owner's knowledge if he finds no other way to obtain it.