Typically these laws would be biased towards the employee. At-will employment pretends there's some sort of symmetry and/or market forces. Social labour laws are about protecting employees, not employers.
Forcing someone to work for two years at a certain place or give 6 months notice before they leave would be considered a violation of their human rights in most places. I'd be really surprised if Germany requires employees to give 6 months notice before leaving...
It depends on your contract. The longest I ever had was 3 months to the end of a quarter. Theses conditons always go both ways. But which employer would insist in keeping you when he knows you want to leave? What level of motivation could he expect?
Forcing someone to work for two years at a certain place or give 6 months notice before they leave would be considered a violation of their human rights in most places. I'd be really surprised if Germany requires employees to give 6 months notice before leaving...