I got hit by another car, but I was try to avoid to contact with the front with improper turn?

Hi, guys. Weeks ago, I got in a car accident. It was a rain day. The front car suddently slow down and stop, and then turn left from an one way road. I was trying to avoid to hit the front car, so I turn my steering wheel, and another truck hit me from behind in another lane. There is a witness who behind me, told the police that the front car didn't turn with a turing singal on. Soon, I'm goin to talk to police about it, and maybe I have to go to court for it. So, what I sould say, and what I should not say. I was frightend, I kind remember he did and later I remember he didin't, I just can't remember very clearer. We r both college students, and he is 19, which one year younger than me. Please, what I should do. Oh, in addition he droven away during the car accident, but he turned a written report to police.