Third Person Controller (Unity)

using UnityEngine;
using System.Collections;

public class ThirdPersonCharaController : MonoBehaviour {

    // Objects
    public GameObject PlayerHolder;

    // Animation Details
    public AnimationClip idleAnimation;
    public AnimationClip walkAnimation;
    public float walkMaxAnimationSpeed = 0.75f;

    // the movement Details
    public float gravity = 20.0f;
    public float moveSpeed = 10.0f;
    public float RotateSpeed = 0.1f;
    public bool LockMovement = false;


    // Private Fields
    private Animation _animation;
    private CharacterController controller;
    private Vector3 moveDirection = Vector3.zero;
    private Vector3 moveVelocity;
    private float oldgravity;
    private float oldRotateSpeed;
    private float new_direction = 0.0f;
    private float rotate_t = 0.0f;


    //=====================================================================
    // Use this for initialization
    void Start () {

        oldRotateSpeed = RotateSpeed;

        oldgravity = gravity;
        _animation = PlayerHolder.GetComponent<Animation>();
        controller = transform.gameObject.GetComponent<CharacterController>();

        if(!_animation)
            Debug.Log("The character you would like to control doesn't have animations. Moving her might look weird.");
        if(!idleAnimation) {
            _animation = null;
            Debug.Log("No idle animation found. Turning off animations.");
        }
        if(!walkAnimation) {
            _animation = null;
            Debug.Log("No walk animation found. Turning off animations.");
        }

    }

    //=====================================================================
    // Updated every Frame
    void Update() {
        if(_animation != null){
            _animation[walkAnimation.name].speed = walkMaxAnimationSpeed;
            _animation.CrossFade(walkAnimation.name);
        }

        if(controller != null && LockMovement == false){
            if (controller.isGrounded) { // Gelandet
                Debug.Log("gelandet");
                moveVelocity = new Vector3(0,0,0);
                if(Input.GetKey(KeyCode.RightArrow) || Input.GetKey(KeyCode.D)) // Rechts
                {
                    if(Input.GetKey(KeyCode.UpArrow) || Input.GetKey(KeyCode.W)){ // Für Diagonale
                        rotate_t = 0.0f;
                        new_direction = 45;
                        moveVelocity = new Vector3(1,0,1);
                    }
                    else if(Input.GetKey(KeyCode.DownArrow) || Input.GetKey(KeyCode.S)){
                        rotate_t = 0.0f;
                        new_direction = 135;
                        moveVelocity = new Vector3(1,0,-1);
                    }
                    else{
                        rotate_t = 0.0f;
                        new_direction = 90;
                        moveVelocity = new Vector3(1,0,0);
                    }
                }
                else if(Input.GetKey(KeyCode.LeftArrow) || Input.GetKey(KeyCode.A)) // Links
                {
                    if(Input.GetKey(KeyCode.UpArrow) || Input.GetKey(KeyCode.W)){ // Für Diagonale
                        rotate_t = 0.0f;
                        new_direction = 315;
                        moveVelocity = new Vector3(-1,0,1);
                    }
                    else if(Input.GetKey(KeyCode.DownArrow) || Input.GetKey(KeyCode.S)){
                        rotate_t = 0.0f;
                        new_direction = 225;
                        moveVelocity = new Vector3(-1,0,-1);
                    }
                    else{
                        rotate_t = 0.0f;
                        new_direction = 270;
                        moveVelocity = new Vector3(-1,0,0);
                    }
                }
                else if(Input.GetKey(KeyCode.UpArrow) || Input.GetKey(KeyCode.W)) // Hoch
                {
                    if(Input.GetKey(KeyCode.LeftArrow) || Input.GetKey(KeyCode.A)){ // Für Diagonale
                        rotate_t = 0.0f;
                        new_direction = 315;
                        moveVelocity = new Vector3(-1,0,1);
                    }
                    else if(Input.GetKey(KeyCode.RightArrow) || Input.GetKey(KeyCode.D)){
                        rotate_t = 0.0f;
                        new_direction = 45;
                        moveVelocity = new Vector3(1,0,1);
                    }
                    else{
                        rotate_t = 0.0f;
                        new_direction = 0;
                        moveVelocity = new Vector3(0,0,1);
                    }
                }
                else if(Input.GetKey(KeyCode.DownArrow) || Input.GetKey(KeyCode.S)) // Runter
                {
                    if(Input.GetKey(KeyCode.LeftArrow) || Input.GetKey(KeyCode.A)){ // Für Diagonale
                        rotate_t = 0.0f;
                        new_direction = 255;
                        moveVelocity = new Vector3(-1,0,-1);
                    }
                    else if(Input.GetKey(KeyCode.RightArrow) || Input.GetKey(KeyCode.D)){
                        rotate_t = 0.0f;
                        new_direction = 135;
                        moveVelocity = new Vector3(1,0,-1);
                    }
                    else{
                        rotate_t = 0.0f;
                        new_direction = 180;
                        moveVelocity = new Vector3(0,0,-1);
                    }
                }

                moveDirection = moveVelocity;
                moveDirection = transform.TransformDirection(moveDirection);
                moveDirection *= moveSpeed;
                gravity = oldgravity;
            }
            else{ // FÄLLT NOCH
                Debug.Log("fällt mit " + gravity);
                gravity += 5.0f;
                gravity = Mathf.Clamp(gravity, oldgravity, oldgravity*2);
            }

            Rotate_to();
            if(Mathf.Abs(PlayerHolder.transform.eulerAngles.y-new_direction) < 35){
                moveDirection.y -= gravity * Time.deltaTime;
                controller.Move(moveDirection * Time.deltaTime);
            }

        }
    }


    //=====================================================================
    float f;
    void Rotate_to(){
        rotate_t += Time.deltaTime * RotateSpeed;
        f = PlayerHolder.transform.eulerAngles.y;
        if (f > 180.0f){
            f -= 360.0f;
        }
        PlayerHolder.transform.eulerAngles = new Vector3(0, Mathf.Lerp(f, new_direction, rotate_t), 0);
    }

//  Vector3 myRotation = Vector3.zero;
//  void Rotate_to(){
//      rotate_t += Time.deltaTime * RotateSpeed;
//      myRotation.y = Mathf.Lerp(myRotation.y, new_direction, rotate_t);
//      PlayerHolder.transform.eulerAngles = myRotation;
//  }
}