How do i move CharacterController toward the direction its facing?

I have a problem with my CharacterController, i already succeed move(forward) the character and rotate it, but i want to the character rotate then when i move it, it'll move forward to the direction its facing

Here's the code for the move

 public void Forward(float vertical_input){
         float forwardSpeed = vertical_input * speed;
 
         if(isGrounded)
             movement = new Vector3 (myBody.velocity.x, 0, forwardSpeed);
             movement = transform.TransformDirection (movement);
         myBody.SimpleMove (movement);
     }

when i rotate the character then move it, the character went to the side (left, right). Before i apply the TransformDirection the character move forward toward its position although i had rotate it. I'm still beginner in Unity, so i don't know much how to handle this, thank you