How to use multiple booleons for an FPS Controller ?,How to control multiple booleons on a single script

I want to make an FPS game and I was trying to write a movement script using bools. it works when I use isGrounded with only one of other bools but when I use multiple bools like Crouch and Run Bools together they just dont want to work together. I dont know why and I really want to learn why they are not working. Here is my code:

 public class RBController : MonoBehaviour
 {
     float moveForward;
     float moveSide;
 
     
 
     private float speed;
     public float crouchSpeed;
     public float slideSpeed;
     public float runSpeed;
     public float defaultSpeed;
     public float JumpSpeed;
 
     Rigidbody rig;
 
     CapsuleCollider PlayerCol;
     float originalHeight;
     public float reducedHeight;
     
     [SerializeField]
     bool isGrounded;
     [SerializeField]
     bool isWalking;
     [SerializeField]
     bool isRunning;
     [SerializeField]
     bool isCrouching;
     [SerializeField]
     bool isSliding;
 
     // Start is called before the first frame update
 
     void Start()
     {
         rig = GetComponent<Rigidbody>();
         speed = defaultSpeed;
         originalHeight = PlayerCol.height;
     }
 
     // Update is called once per frame
     void Update()
     {
         moveForward = Input.GetAxis("Vertical") * speed;
         moveSide = Input.GetAxis("Horizontal") * speed;
 
         rig.velocity = (transform.forward * moveForward) + (transform.right * moveSide) + (transform.up * rig.velocity.y);
 
         //Sprint
         if (Input.GetKey(KeyCode.LeftShift) && isGrounded)
         {
             isRunning = true;
         }
         else
         {
             isRunning = false;
         }
 
         if (isRunning)
         {
             Run();
         }
         else if (!isRunning)
         {
             Walk();
         }
 
         //Crouch
         if (Input.GetKey(KeyCode.LeftControl))
         {
             isCrouching = true;
         }
         else
         {
             isCrouching = false;
         }
 
         if (isCrouching)
         {
             Crouch();
         }
         else if (!isCrouching)
         {
             GoUp();
         }
     }
 
     void Run()
     {
         speed += runSpeed;
         isCrouching = false;
     }
     void Walk()
     {
         speed = defaultSpeed;
     }
     void Crouch()
     {
         speed = crouchSpeed;
         PlayerCol.height = reducedHeight;
     }
     void GoUp()
     {
         isCrouching = false;
         speed = defaultSpeed;
         PlayerCol.height = originalHeight;
     }
 
     private void OnCollisionEnter(Collision col)
     {
         if(col.gameObject.tag == "Ground")
         {
             isGrounded = true;
         }
     }
     private void OnCollisionExit(Collision col)
     {
         if(col.gameObject.tag == "Ground")
         {
             isGrounded = false;
         }
     }
 }