I have a problem in the jump system.

You could always use the Unity standard assets to get the player movement script, but I understand if you are simply trying to make your own. You will need the camera to be inside the player movement object and have the camera tagged as main camera. The unity standard assets script for movement is as follows:

 using System;
 using UnityEngine;
 using UnityStandardAssets.CrossPlatformInput;
 using UnityStandardAssets.Utility;
 using Random = UnityEngine.Random;
 
 namespace UnityStandardAssets.Characters.FirstPerson
 {
     [RequireComponent(typeof (CharacterController))]
     [RequireComponent(typeof (AudioSource))]
     public class FirstPersonController : MonoBehaviour
     {
         [SerializeField] private bool m_IsWalking;
         [SerializeField] private float m_WalkSpeed;
         [SerializeField] private float m_RunSpeed;
         [SerializeField] [Range(0f, 1f)] private float m_RunstepLenghten;
         [SerializeField] private float m_JumpSpeed;
         [SerializeField] private float m_StickToGroundForce;
         [SerializeField] private float m_GravityMultiplier;
         [SerializeField] private MouseLook m_MouseLook;
         [SerializeField] private bool m_UseFovKick;
         [SerializeField] private FOVKick m_FovKick = new FOVKick();
         [SerializeField] private bool m_UseHeadBob;
         [SerializeField] private CurveControlledBob m_HeadBob = new CurveControlledBob();
         [SerializeField] private LerpControlledBob m_JumpBob = new LerpControlledBob();
         [SerializeField] private float m_StepInterval;
         [SerializeField] private AudioClip[] m_FootstepSounds;    // an array of footstep sounds that will be randomly selected from.
         [SerializeField] private AudioClip m_JumpSound;           // the sound played when character leaves the ground.
         [SerializeField] private AudioClip m_LandSound;           // the sound played when character touches back on ground.
 
         private Camera m_Camera;
         private bool m_Jump;
         private float m_YRotation;
         private Vector2 m_Input;
         private Vector3 m_MoveDir = Vector3.zero;
         private CharacterController m_CharacterController;
         private CollisionFlags m_CollisionFlags;
         private bool m_PreviouslyGrounded;
         private Vector3 m_OriginalCameraPosition;
         private float m_StepCycle;
         private float m_NextStep;
         private bool m_Jumping;
         private AudioSource m_AudioSource;
 
         private void Start()
         {
             m_CharacterController = GetComponent<CharacterController>();
             m_Camera = Camera.main;
             m_OriginalCameraPosition = m_Camera.transform.localPosition;
             m_FovKick.Setup(m_Camera);
             m_HeadBob.Setup(m_Camera, m_StepInterval);
             m_StepCycle = 0f;
             m_NextStep = m_StepCycle/2f;
             m_Jumping = false;
             m_AudioSource = GetComponent<AudioSource>();
             m_MouseLook.Init(transform , m_Camera.transform);
         }
 
         private void Update()
         {
             RotateView();
             if (!m_Jump)
             {
                 m_Jump = CrossPlatformInputManager.GetButtonDown("Jump");
             }
 
             if (!m_PreviouslyGrounded && m_CharacterController.isGrounded)
             {
                 StartCoroutine(m_JumpBob.DoBobCycle());
                 PlayLandingSound();
                 m_MoveDir.y = 0f;
                 m_Jumping = false;
             }
             if (!m_CharacterController.isGrounded && !m_Jumping && m_PreviouslyGrounded)
             {
                 m_MoveDir.y = 0f;
             }
 
             m_PreviouslyGrounded = m_CharacterController.isGrounded;
         }
 
 
         private void PlayLandingSound()
         {
             m_AudioSource.clip = m_LandSound;
             m_AudioSource.Play();
             m_NextStep = m_StepCycle + .5f;
         }
 
 
         private void FixedUpdate()
         {
             float speed;
             Vector3 desiredMove = transform.forward*m_Input.y + transform.right*m_Input.x;
             RaycastHit hitInfo;
             Physics.SphereCast(transform.position, m_CharacterController.radius, Vector3.down, out hitInfo,
                                m_CharacterController.height/2f, Physics.AllLayers, QueryTriggerInteraction.Ignore);
             desiredMove = Vector3.ProjectOnPlane(desiredMove, hitInfo.normal).normalized;
 
             m_MoveDir.x = desiredMove.x*speed;
             m_MoveDir.z = desiredMove.z*speed;
 
 
             if (m_CharacterController.isGrounded)
             {
                 m_MoveDir.y = -m_StickToGroundForce;
 
                 if (m_Jump)
                 {
                     m_MoveDir.y = m_JumpSpeed;
                     PlayJumpSound();
                     m_Jump = false;
                     m_Jumping = true;
                 }
             }
             else
             {
                 m_MoveDir += Physics.gravity*m_GravityMultiplier*Time.fixedDeltaTime;
             }
             m_CollisionFlags = m_CharacterController.Move(m_MoveDir*Time.fixedDeltaTime);
 
             ProgressStepCycle(speed);
             UpdateCameraPosition(speed);
 
             m_MouseLook.UpdateCursorLock();
         }
 
 
         private void PlayJumpSound()
         {
             m_AudioSource.clip = m_JumpSound;
             m_AudioSource.Play();
         }
 
 
         private void ProgressStepCycle(float speed)
         {
             if (m_CharacterController.velocity.sqrMagnitude > 0 && (m_Input.x != 0 || m_Input.y != 0))
             {
                 m_StepCycle += (m_CharacterController.velocity.magnitude + (speed*(m_IsWalking ? 1f : m_RunstepLenghten)))*
                              Time.fixedDeltaTime;
             }
 
             if (!(m_StepCycle > m_NextStep))
             {
                 return;
             }
 
             m_NextStep = m_StepCycle + m_StepInterval;
 
             PlayFootStepAudio();
         }
 
 
         private void PlayFootStepAudio()
         {
             if (!m_CharacterController.isGrounded)
             {
                 return;
             }
 
             int n = Random.Range(1, m_FootstepSounds.Length);
             m_AudioSource.clip = m_FootstepSounds[n];
             m_AudioSource.PlayOneShot(m_AudioSource.clip);
 
             m_FootstepSounds[n] = m_FootstepSounds[0];
             m_FootstepSounds[0] = m_AudioSource.clip;
         }
 
 
         private void UpdateCameraPosition(float speed)
         {
 
             Vector3 newCameraPosition;
             if (!m_UseHeadBob)
             {
                 return;
             }
             if (m_CharacterController.velocity.magnitude > 0 && m_CharacterController.isGrounded)
             {
                 m_Camera.transform.localPosition =
                     m_HeadBob.DoHeadBob(m_CharacterController.velocity.magnitude +
                                       (speed*(m_IsWalking ? 1f : m_RunstepLenghten)));
                 newCameraPosition = m_Camera.transform.localPosition;
                 newCameraPosition.y = m_Camera.transform.localPosition.y - m_JumpBob.Offset();
             }
             else
             {
                 newCameraPosition = m_Camera.transform.localPosition;
                 newCameraPosition.y = m_OriginalCameraPosition.y - m_JumpBob.Offset();
             }
             m_Camera.transform.localPosition = newCameraPosition;
         }
 
 
         private void GetInput(out float speed)
         {
             float horizontal = CrossPlatformInputManager.GetAxis("Horizontal");
             float vertical = CrossPlatformInputManager.GetAxis("Vertical");
 
             bool waswalking = m_IsWalking;
 
 #if !MOBILE_INPUT
             m_IsWalking = !Input.GetKey(KeyCode.LeftShift);
 #endif
 
             speed = m_IsWalking ? m_WalkSpeed : m_RunSpeed;
             m_Input = new Vector2(horizontal, vertical);
 
             if (m_Input.sqrMagnitude > 1)
             {
                 m_Input.Normalize();
             }
 
             if (m_IsWalking != waswalking && m_UseFovKick && m_CharacterController.velocity.sqrMagnitude > 0)
             {
                 StopAllCoroutines();
                 StartCoroutine(!m_IsWalking ? m_FovKick.FOVKickUp() : m_FovKick.FOVKickDown());
             }
         }
 
 
         private void RotateView()
         {
             m_MouseLook.LookRotation (transform, m_Camera.transform);
         }
 
 
         private void OnControllerColliderHit(ControllerColliderHit hit)
         {
             Rigidbody body = hit.collider.attachedRigidbody;
             //dont move the rigidbody if the character is on top of it
             if (m_CollisionFlags == CollisionFlags.Below)
             {
                 return;
             }
 
             if (body == null || body.isKinematic)
             {
                 return;
             }
             body.AddForceAtPosition(m_CharacterController.velocity*0.1f, hit.point, ForceMode.Impulse);
         }
     }
 }