There is a probationary period for both indefinite and fixed-term employment contracts. This applies to both you and the university. The probationary period for an employment contract of more than 6 months can be up to 2 months at most. The duration is mentioned in your employment contract.
Legally, a probationary period can be agreed upon for each first employment contract in a given position. This means that if you move to a clearly different position, you have to go through another probationary period. Both the employer and the employee can terminate the employment contract during the probationary period. For this, no notice period needs to be taken into account and no reason for termination needs to be provided, in principle.