Player keeps flying up

Hey there! I'm a complete noob in unity and coding and want to make my first own game. I almost finished my movement script and everything works fine. Now i wanted to add a fall animation when the character is not grounded for more than 2 seconds. However, when the fall animation starts, the player seems to lose its gravity and flies up infinitely and I'm having a hard time figuring out why that is. Anyway, here's my script (fall animation is anim integer "AnimPara" = 5):

 public class PlayerMovement : MonoBehaviour {
 
     public float walkBackSpeed = 2f;
     public float walkSpeed = 4f;
     public float runSpeed = 10f;
     public float turnSpeed = 50f;
     public float jumpSpeed = 8f;
     public float speed;
     public float timeTilFall;
     public Animator anim;
 
     private Vector3 moveJump = Vector3.zero;
     private Vector3 moveDir = Vector3.zero;
     private CharacterController controller;
     
 
     void Start () {
         controller = gameObject.GetComponentInChildren<CharacterController>();
         anim = gameObject.GetComponentInChildren<Animator>();
         
     }
     
     void Update () {
 
 
 
         if (Input.GetKey("w"))
         {
             anim.SetInteger("AnimPara", 2);
             speed = walkSpeed;
             if (Input.GetKeyDown("space"))
             {
                 anim.SetInteger("AnimPara", 3);
             }
             if (Input.GetKey("left shift"))
             {
                 anim.SetInteger("AnimPara", 1);
                 speed = runSpeed;
             }
             if (Input.GetKey("s"))
             {
                 anim.SetInteger("AnimPara", 0);
                 speed = 0;
             }
         }
         else if (Input.GetKeyDown("space") && controller.isGrounded)
         {
             anim.SetInteger("AnimPara", 3);
         }
         else if(Input.GetKey("s"))
         {
             anim.SetInteger("AnimPara", 4);
             speed = walkBackSpeed;
         }
         else if (Input.GetKey("s"))
         {
             if (Input.GetKey("w"))
             {
                 anim.SetInteger("AnimPara", 0);
                 speed = 0;
             }
             
         }
         else
         {
             anim.SetInteger("AnimPara", 0);
         }
 
         if (controller.isGrounded)
         {
             anim.SetBool("IsGrounded", true);
             moveDir = transform.forward * Input.GetAxis("Vertical") * speed;
             moveJump = transform.up * Input.GetAxis("Jump") * jumpSpeed;
             timeTilFall = 0;
         }
         else
         {
             timeTilFall += 1 * Time.deltaTime;
             if (timeTilFall > 2 && anim.GetInteger("AnimPara")!=5)
             {
                 anim.SetInteger("AnimPara",5);
             }
         }
         Debug.Log(timeTilFall);
         float turn = Input.GetAxis("Horizontal");
         float jump = Input.GetAxis("Jump");
         transform.Rotate(0, turn * turnSpeed * Time.deltaTime, 0);
         controller.Move(moveDir * Time.deltaTime);
         controller.Move(moveJump * Time.deltaTime);
     }