Lots to learn and most has been discussed endlessly.
Lambda control in closed loop exists for O2 voltages between .2 and .8v for MBs. Some cars use 5v O2 sensors but not MB.
Duty cycle refers to the level of correction when viewed dynamically. Middle of range would be 50%. Duty cycle as a constant is used as a fault code.
Bosch Master, ASE Master, L1
33 years MB technician