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While I coming reverse, the back bottom side of my car damaged when it hit the car at back.

My backside of car crashed while coming reverse as it stroke the car at back.

Could you please let me know if the sentences are correct?

Also any colloquial way to express the same.
Comments 
in reverse
was damaged
at back behind
While I coming reverse, the back bottom side of my car damaged when it hit the car at back.

My backside of car crashed while coming reverse as it stroke the car at back.

Could you please let me know if the sentences are correct?

Also any colloquial way to express the same.
I damaged my car, because I reversed into the car behind me.

Clive
My car was damaged when I accidentally backed into the car behind me.

CJ