Can you bring a car back after 9 days? This information is important because tomorrow will be day 9 any information will help.

? Was there some 9 day return in the contract that you signed?

Most car sales are final.

1. what country is it
2. new car or used car
3. was it bought as is or was there a warranty
4. why do you want to return it
5 does the contract give you any right to return it

Depends if it's new or not. There are these things called lemon laws that cover a new car but I'm not all too sure how they work. Maybe try googling them.
The purchase of a used car probably isn't so protected.