Add terrain collision and fix axis of camera

I made 3rd person camera script which works ok but needs few tweaks which I don't know how to fix. I'm using controller/ joystick.

-Firstly, camera has this issue: when I look at the back of the player and move him forward, he goes forward (which is ok). But when I look at the player sideways or from the front (let's say from the front side) when I move player forward he goes towards the camera instead of to the opposite side from where the camera is.

So basically, player's movements are always the same (left is left, forward is forward) no matter where the camera is...and that is what I want to fix. I'm not even sure if this is camera problem at all, maybe Movement Script?

-Secondly, I want camera to collide with terrain and objects in the world.

This is my script so far:

  using UnityEngine;
     using System.Collections;
     
     public class PlayerScript : MonoBehaviour
     {
         public float RotateSpeed = 150,
         MoveSpeed = 50;
         float DeltaTime;
         
         void Update()
         {
             DeltaTime = Time.deltaTime;
             transform.Rotate(0, Input.GetAxis("LeftX") * RotateSpeed * DeltaTime, 0);
             transform.Translate(0, 0, -Input.GetAxis("LeftY") * MoveSpeed * DeltaTime);
         }
     }
     
     public class CameraScript : MonoBehaviour
     {
         public GameObject Target;
         public float RotateSpeed = 170,
         FollowDistance = 20,
         FollowHeight = 10;
         float RotateSpeedPerTime,
         DesiredRotationAngle,
         DesiredHeight,
         CurrentRotationAngle,
         CurrentHeight,
         Yaw,
         Pitch;
         Quaternion CurrentRotation;
         
         void LateUpdate()
         {
             RotateSpeedPerTime = RotateSpeed * Time.deltaTime;
             
             DesiredRotationAngle = Target.transform.eulerAngles.y;
             DesiredHeight = Target.transform.position.y + FollowHeight;
             CurrentRotationAngle = transform.eulerAngles.y;
             CurrentHeight = transform.position.y;
             
             CurrentRotationAngle = Mathf.LerpAngle(CurrentRotationAngle, DesiredRotationAngle, 0);
             CurrentHeight = Mathf.Lerp(CurrentHeight, DesiredHeight, 0);
             
             CurrentRotation = Quaternion.Euler(0, CurrentRotationAngle, 0);
             transform.position = Target.transform.position;
             transform.position -= CurrentRotation * Vector3.forward * FollowDistance;
             transform.position = new Vector3(transform.position.x, CurrentHeight, transform.position.z);
             
             Yaw = Input.GetAxis("Right Horizontal") * RotateSpeedPerTime;
             Pitch = Input.GetAxis("Right Vertical") * RotateSpeedPerTime;
             transform.Translate(new Vector3(Yaw, -Pitch, 0));
             transform.position = new Vector3(transform.position.x, transform.position.y, transform.position.z);
             
             transform.LookAt(Target.transform);
         }
     }