Plea bargains (Verständigung in Strafsachen, § 257c StPO) happen in Germany, but not in murder cases, though a sentence might be reduced for a cooperative accused. They are more common in complicated financial crimes or small scale crimes like theft. There’s also a limited frame in which the judge decides on the punishment, it would be extremely odd that a potential sentence of 30 years is reduced to 2 years. Having less extreme prison sentences and a right to a paid lawyer reduces the pressure on the defendant.