Flip an object by 180° (C#)

Hi, I'm very new to Unity and I didn't find a working answer to a 180 degrees rotation problem I have.

I refer to a part of game similar to a function in transport tycoon, simutrans etc,

I need to have a behaviour like this: the object starts from point A, goes to point B, then to point C and goes there and back again between B and C in infinite loop - a vehicle that exits from its depot, goes to the load point, then to the delivery point, then the load point and so on.

This is my code:

 using UnityEngine;
 using System;
 using System.Collections;
 
 public class VehicleBehaviour : MonoBehaviour
 {
     public Vector3 StartDestination;
     public Vector3 EndDestination;
     public Vector3 StartingPosition;
     public bool StraightDirection;
     public Vehicle v;
     bool rotating = false;
     Vector3 angle;
         
     IEnumerator Start()
     {
         if (StraightDirection)
         {
             StartingPosition = (StartingPosition.x != 0.0f && StartingPosition.y != 0.0f && StartingPosition.z != 0.0f) ? StartingPosition : StartDestination;
             yield return StartCoroutine(Move (transform, StartingPosition, EndDestination, v.Speed, -1));
         }
         else
         {
             StartingPosition = (StartingPosition.x != 0.0f && StartingPosition.y != 0.0f && StartingPosition.z != 0.0f) ? StartingPosition : EndDestination;
             yield return StartCoroutine(Move (transform, StartingPosition, StartDestination, v.Speed, 1));
         }
         StraightDirection = !StraightDirection;
         while (true) {
                 yield return StartCoroutine(Move(transform, EndDestination, StartDestination, v.Speed, -1));
                 yield return StartCoroutine(Move(transform, StartDestination, EndDestination, v.Speed, 1));
         }
     }
     
     IEnumerator Move(Transform thisTransform, Vector3 startPos, Vector3 endPos, float time, int d)
     {
         float i= 0.0f;
         float rate= 1.0f/time;
         float ang1 = Vector3.Angle (d*(startPos - endPos), -d * thisTransform.forward);
         thisTransform.eulerAngles = new Vector3 (0, ang1, 0);
         angle = thisTransform.eulerAngles;
         while (i < 1.0f) {
             i += Time.deltaTime * rate;
             thisTransform.position = Vector3.Lerp(startPos, endPos, i);
             thisTransform.position = thisTransform.position + new Vector3(0f, Terrain.activeTerrain.SampleHeight (transform.position) + renderer.bounds.size.y/2 + v.Distance, 0f);
             yield return null;
         }
         float ang2 = Vector3.Angle (d*(endPos - startPos), -d * thisTransform.forward);
 
         thisTransform.eulerAngles = new Vector3 (thisTransform.eulerAngles.x, ang2, thisTransform.eulerAngles.z);
 
     }

 }

(I've omitted some {if..then} here and there).

With this code I've obtained my vehicle to go correctly forward and "shift to reverse" instead of turning by 180°.

Among all my attempts I tried to modify this part "thisTransform.eulerAngles = new Vector3 (thisTransform.eulerAngles.x, ang2, thisTransform.eulerAngles.z);" in a thousand differnt ways and it seems that this should be the line to change (I've tried from the most obvious "-ang2" to a lot of code taken here and there in unityAnswers in many answers -as in example: how to get the positive or negative angle and How can I rotate an object 180 degrees? (C#)-).

Thnks in advice for help :)