You are required to have health insurance in germany. If you choose private you often get better service (which technically is illegal) but you can save money when you are young and can only leave and move back to public until a certain age. Most people just have public health care since that is safer since you dont have to upfront costs. You are always insured, no matter your state of employment. (theoretically at least, some people fall through the net but that is a different topic)