You are driving on a one-way street with signposting. What is correct?

Your answer is fully correct.

When driving in a one-way street (Einbahnstraße), you must position your vehicle as far to the left as possible if you plan to turn left. This ensures a safe and clear turning maneuver without obstructing other traffic.

Also, parking on the left-hand side of the road is allowed because the traffic flows only in one direction, making it safer to park on both sides compared to a two-way street where parking against traffic flow would be dangerous or illegal.

However, parking against the direction of traffic (option 3) is not allowed because in a one-way street, all traffic moves in the same direction, and parking must follow that direction to avoid hazards or confusion.

Remember, the key rule is that in a one-way street, traffic direction and related maneuvers must respect the flow indicated by signs, including parking and turning.