i was playing the game and was at the auction house and was bidding on multipule cars and was then banned lost over 15 cars i had already won and over 100 million credits PLEASE HELP
You should maybe take a look at the sticky thread at the top of this very forum regarding title-specific bans.
Unfortunately, once you're banned from a Forza title, you are banned for good.
Turn10 do NOT partake in relaying the information that you are asking for, so there's simply no use in asking them.
I'm sorry to hear your loss, as a notable portion of the community have also been banned for unknown reasons.