You keep your job at the company, but your working place may change. The working contract is still valid. The parents can stay at home with their children for up to three years per child and they can choose how to divide this time between them. During that period, the working contract cannot be cancelled. The job has to be the same one or a an equal one after the parent returns to the job. If you had a fulltime job before, you will get a fulltime job now. But you have no right to the exact job / position / working desk you had before.
For further information see:
https://www.eltern.de/familie-urlaub/beruf/zurueck-den-job-das-sind-ihre-rechte/page/2