'get off' vs 'get down from'

[Daemon99]

1) He got off the car at Baker's Street.
2) He got down from the car at Baker's Street.
3) He got out of the car at Baker's Street.

4) He got off the bus/train/aeroplane at Baker's Street.
5) He got down from the bus/train/aeroplane at Baker's Street.
6) He got out of the bus/train/aeroplane at Baker's Street.

Can someone please tell me which of the above sentences are correct? When do we use get off and when get down from? Also, can I use get off from in place of get off?
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Non-native speaker of English
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I intend to live forever - so far, so good.

[Kitosdad]

He got out of the car at Baker's Street.

He got off the bus at Baker's Street.

We get off a bus or plane.

We get down from a high place, like a roof or from a ladder.
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Keep it simple ... Keep it interesting.

[Daemon99]

Thanks mate! Another question. Which of the following sentences sounds natural?

Can you stop the car here? I want to get down.
Can you stop the car here? I want to get off.
Can you stop the car here? I want to get out.

When I say "I want to get off the car", does it mean I am sitting on its roof?
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Non-native speaker of English
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I intend to live forever - so far, so good.

[Skrej]