Can the employer change the tasks agreed on in the employment contract by invoking their supervisory rights?

The employment contract may specify the tasks in general or in very detailed terms. The more detailed the task description, the less right the employer has to change it.

In addition to the actual work task, the employment contract may include a reference to "other tasks assigned by the supervisor". However, this clause cannot change the content of the main work task without following the arrangements for changing the terms of the employment contract. This usually means that the employer must have either production-related, financial or person-related reasons for the termination. These are explained in Chapter 7 of the Employment Contracts Act.