Both the convict and the victim were working at the restaurant when the 39-year-old attacked the colleague with a knife.
According to the district court's verdict, there was "danger to the completion of the crime".
The victim was stabbed in both the head and back, and the head injury is said to have been life-threatening.
The 39-year-old has denied that his intention was to kill.
He has also not been able to state why he attacked with the knife.
The district court decided on a forensic psychiatric investigation and it concluded that the 39-year-old suffered from a serious mental disorder.
He is therefore sentenced to forensic psychiatric care.
The penalty value for the crime corresponds to a prison sentence of around ten years, according to the verdict.