der Rückwärtsgang
reverse gear
The gear in a vehicle that makes it possible to drive backward.
Der Fahrer legte den Rückwärtsgang ein, um einzuparken.
The driver put the car into reverse gear in order to park.

reverse gear
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reverse gear
The gear in a vehicle that makes it possible to drive backward.
Der Fahrer legte den Rückwärtsgang ein, um einzuparken.
The driver put the car into reverse gear in order to park.

The word is made up of three parts: 'rückwärts' (backward), the linking sound '-s-', and 'Gang' (gear). So it literally means a 'gear' with which you drive 'backward'.
Beim Einparken muss man den Rückwärtsgang benutzen.
When parking, you have to use reverse gear.
The fixed expression for both meanings is 'den Rückwärtsgang einlegen' (to put into reverse gear). This applies both to driving a car and to a figurative step backward.
Um aus der Parklücke zu kommen, musste er den Rückwärtsgang einlegen.
To get out of the parking space, he had to put the car into reverse gear.
You can tell whether the literal or figurative meaning is intended from the context. If it is about vehicles and driving, the technical meaning is meant. If it is about politics, society, or development, it means a step backward.
Das Getriebe ist kaputt, ich kann den Rückwärtsgang nicht mehr einlegen.
The transmission is broken; I can't put it into reverse gear anymore.
progress
'der Fortschritt' and 'der Rückwärtsgang' are opposites in a figurative sense. 'Fortschritt' means that something is moving forward or getting better. 'Rückwärtsgang' means figuratively that a development is going backward again or that earlier improvements are being lost. The word originally comes from cars, but it is also used for politics, work, or personal development. Put simply: 'Fortschritt' goes forward; 'Rückwärtsgang' goes backward.

Mit dieser Entscheidung legt die Stadt beim Klimaschutz den Rückwärtsgang ein.
With this decision, the city is shifting into reverse on climate protection.
Neue Ideen bringen in der Firma viel Fortschritt.
New ideas bring a lot of progress to the company.