What must you do in this situation?

You answered correctly by choosing to brake immediately and not to swerve. In German traffic rules, when faced with a sudden hazard or danger, the safest action is to reduce speed as quickly as possible by braking firmly. Swerving abruptly to the left or right is generally not recommended because it may lead to losing control of the vehicle, endangering yourself and others, especially on rural roads where oncoming traffic or roadside obstacles may be present. Maintaining a straight path while braking ensures maximum stability and control. This approach helps prevent accidents by giving you better control and space to respond safely to the situation.