Entry from any third country is possible for travelers who can demonstrate an important reason for their travel. The list of important reasons covers German and EU citizens and any third-country nationals with a right of residency in Germany. It also includes healthcare and health researchers, skilled workers whose economic activity is necessary and cannot be postponed or performed from abroad, freight and transport staff, seasonal workers, students who cannot continue their studies from abroad, travelers making visits for urgent family reasons, diplomats and staff at international organizations, and persons transiting Germany. Quarantine requirements in Germany differ depending on the German state.
All travelers arriving from high-risk areas (over 50 cases per 100,000 inhabitants) are required to stay in quarantine for 14 days on arrival in Germany. The quarantine requirement does not apply to travelers in transit through Germany who show no symptoms of infection with COVID-19, or to people who have a doctor's certificate stating that they show no signs of infection. This must come from a doctor in an EU member state or in a country listed on
this site, and it must have been issued within the past 48 hours.
More information can be found
here.