FreeLookCamera.cs

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

[RequireComponent(typeof(Camera))]
public class CameraManouver : MonoBehaviour
{
    Transform _transform; // cache transform component of the camera
    [Header("Keyboard Translation")]
    public float horizontalFactor = 10f;
    public float verticalFactor = 10f;

    [Header("Mouse Camera Look")]
    public float mouseSensitivity = 100.0f;
    [Tooltip("Range of motion around the X axis, up and down between [-value, value]")]
    public float clampAngle = 80.0f;
    private float rotY = 0.0f; // rotation around the up/y axis == Left vs Right (sideways)
    private float rotX = 0.0f; // rotation around the right/x axis == Up vs Down (Vertically)
    
    // Start is called before the first frame update
    void Start()
    {
        _transform = GetComponent<Transform>();
        Vector3 rot = _transform.localRotation.eulerAngles;
        rotY = rot.y;
        rotX = rot.x;
    }

    // Update is called once per frame
    void Update()
    {
        // Keyboard Translation ==================
        
        var haxis = Input.GetAxis("Horizontal");
        var vaxis = Input.GetAxis("Vertical");
        
        _transform.Translate(haxis * Vector3.right * horizontalFactor * Time.deltaTime, Space.Self);
        _transform.Translate(vaxis * Vector3.forward * verticalFactor * Time.deltaTime, Space.Self);
        
        // Mouse Free Look ========================

        float mouseX = Input.GetAxis("Mouse X");
        float mouseY = -Input.GetAxis("Mouse Y");

        rotY += mouseX * mouseSensitivity * Time.deltaTime;
        rotX += mouseY * mouseSensitivity * Time.deltaTime;

        rotX = Mathf.Clamp(rotX, -clampAngle, clampAngle);

        Quaternion localRotation = Quaternion.Euler(rotX, rotY, 0.0f);
        transform.rotation = localRotation;
        //:::::::::
    }
}