playerMovement.cs

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

public class PlayerMovement : MonoBehaviour
{
    public CharacterController controller;

    public float speed;
    public float gravity = -19.81f; //default gravity
    public float jumpHeight = 3f;

    public Transform groundCheck; //invisible object on player's feet
    public float groundDistance = 0.2f; //radius of the invisible sphere
    public LayerMask groundMask; //controlling which objects the sphere should check for, so that it doesnt check isGrounded as true when standing on the player

    Vector3 velocity;
    bool isGrounded;

    // Update is called once per frame
    void Update()
    {
        isGrounded = Physics.CheckSphere(groundCheck.position, groundDistance, groundMask);
        //creates a tiny invisible sphere on player's foot with specified radius groundDistance, and if it collides with anything in groundMask, then isGrounded will set to true, if not, then false

        if (isGrounded && velocity.y < 0)
        {
            velocity.y = -2f; //not 0 but -2 is because if incase it sets true too soon, it makes the player force on ground properly
        }

        float x = Input.GetAxis("Horizontal"); //getaxis function gives 1 if right key is pressed
        float z = Input.GetAxis("Vertical"); //1 if forwards key is pressed

        /* first dumb idea - https://pastebin.com/CFXXtY8s*/

        Vector3 move = (transform.right * x + transform.forward * z) * speed; //transform right is red arrow vector, from -1 to 1, forward is blue axis
        //those arrows are multiplied by x or z, which are 0 if nothing is pressed or 1 if wasd is pressed
        //then its added together, forming a vector pointing to the direction where i wanna go
        //and multiplied by the speed constant

        controller.Move(move * Time.deltaTime);


        /*first dumb idea  - gravity multiplier makes it grow more each time, but its would be better to square the velocity by gravity multiplier so it grows exponencialy
        velocity = velocity * gravityMultiplier;
        gravityMultiplier++;*/

        if (Input.GetButtonDown("Jump") && isGrounded) //jumping
        {
            velocity.y = Mathf.Sqrt(jumpHeight * -2f * gravity); //why? physics https://imgur.com/a/BQMlYuj
        }

        velocity.y = velocity.y + gravity * Time.deltaTime;
        controller.Move(velocity * Time.deltaTime);
        //2x delta time - ^2, and why its like this - physics https://imgur.com/a/ulUTu7D

        //Debug.Log("transform.right " + transform.right);
        //Debug.Log("x " + x);
        //Debug.Log("transform.forward" + transform.forward);
        //Debug.Log("z " + z);
        //Debug.Log("move " + move);

    }
}