Unity3d player jump with character controller bug

See more:

C#

Unity3D

So i have a script that moves my player plays the animations as needed and jumps.
But there are 2 problems.
1. On idle my characters speed is 0 but where i run the game the speed when i dont move the player goes 0 then 10 then 0 then 10 again, and is this loop of increase and decrease of speed, and the animation for slow run is playing in a buggy way.

2. My jump height is controlled by how fust i am running. I have 3 states of my character,
Idle, SlowRun, FastRun,when i SlowRun then it jumps normal but when i FastRun the jump height is higher.
I will paste my entire code bellow, thank you.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class playermovement : MonoBehaviour
{
    private CharacterController controller;
    public float playerSpeed = 0;
    public float gravity = 5f;
    public float jumpSpeed = 5f;
    private Vector3 move = Vector3.zero;
    private Animator anim;

    private float verticalVelocity;

    private void Start()
    {
        controller = GetComponent<CharacterController>();
        anim = GetComponentInChildren<Animator>();
    }

    void Update()
    {
        Move();
    }

    private void Move()
    {
        
        if (controller.isGrounded)
        {
            float horizontal = Input.GetAxis("Horizontal");
            float vertical = Input.GetAxis("Vertical");

            move = new Vector3(horizontal, 0, vertical);
            move = transform.TransformDirection(move);
        }

        if (move == Vector3.zero)
        {
            Idle();
        }
        else if (move != Vector3.zero && !Input.GetKey(KeyCode.LeftShift))
        {
            SlowRun();

        }
        else if (move != Vector3.zero && Input.GetKey(KeyCode.LeftShift))
        {
            FastRun();
        }

        if (Input.GetKeyDown(KeyCode.Space))
        {
            move.y = jumpSpeed;
        }

        move.y -= gravity * Time.deltaTime;
        controller.Move(move * Time.deltaTime * playerSpeed);
    }

    private void Idle()
    {
        playerSpeed = 0;
        anim.SetFloat("Speed", 0, 0.1f, Time.deltaTime);
    }

    private void SlowRun()
    {
        playerSpeed = 10f;
        anim.SetFloat("Speed", 0.5f, 0.1f, Time.deltaTime);
    }

    private void FastRun()
    {
        playerSpeed = 20f;
        anim.SetFloat("Speed", 1, 0.1f, Time.deltaTime);
    }
}

What I have tried:

I cant figure out why it does this, I have gone online, whatched a lot of videos but i have no idea. I have tried having 2 CharacterController.Move() functions but the it becomes a mess, atleast for my knowledge of c#.
When i say a mess, i mean that then the jump function doesnt work all the time and when i am near a building or steps i get thrown high up like of the map when i press the jump button.
I can not use LayerMask beacuse i need the enviroment to have different layers for other stuff i want to do.
Thank you.