How it is supposed to work is that 50% of representatives are 'local' representing a region (of roughly 300.000 people) and the remaining 50% of representatives ensure proportionality.
So, imagine the CDU (centre-right party) wins 40% of the voting share, but 60% of the seats, the SPD (centre-left) 30% of both voting share, and seats, the Greens 20% of the share but only 10% of the seats, and the FDP 10% of the share and no seats. The seats to ensure proportionality would be distributed 20%, 30%, 30%, 20% respectively.
There are a lot of subtleties to the system to ensure true proportionality that I won't go into right now, and tend to lead to the parliament growing (if things work perfectly there should be 598 seats, but currently there are 736), but broadly the system works.
How it is supposed to work is that 50% of representatives are 'local' representing a region (of roughly 300.000 people) and the remaining 50% of representatives ensure proportionality.
So, imagine the CDU (centre-right party) wins 40% of the voting share, but 60% of the seats, the SPD (centre-left) 30% of both voting share, and seats, the Greens 20% of the share but only 10% of the seats, and the FDP 10% of the share and no seats. The seats to ensure proportionality would be distributed 20%, 30%, 30%, 20% respectively.
There are a lot of subtleties to the system to ensure true proportionality that I won't go into right now, and tend to lead to the parliament growing (if things work perfectly there should be 598 seats, but currently there are 736), but broadly the system works.