I got a subpoena to testify im scared to go though?

[Jennifer]

Im suppos to testify for my ex boyfriend whom before i told the police he stole my car , im scared because i had lied to the police but they dont know i did, but i actually let him borrow my car but i called the police because he wasnt there with the car when i went to his house to go get it i dont know what kind of questions their going to ask me