"All Germans shall have the right to move freely throughout the federal territory."
Article 11 says that all German citizens can travel freely and live wherever they want within Germany. But there is one exception: if somewhere is unsafe, for instance, the state can prohibit people from going there. The state can also require people with an infectious disease to remain in quarantine for a while.
Article 11 is a civil right, so it only applies to German citizens. Citizens of other EU countries are also entitled to such freedom, as freedom of movement is established within the EU law.