How to use Look-at using only 2 axis to rotate.

Hi, I want to begin by saying that I did search and found for answers about this topic in the past and I also tried multiple times to apply the answers I found.

Sadly I still have issues to constrain the rotation on the z axis :(

We are lucky though as I can show you guys my code and a video of the issue !

(note that the z axis I talk about is pointing down for the character feets , I want to point with my feets but not rotate left and right while doing so) First of here is my code for the look-at:

             float oldZ = transform.rotation.z;
 
             playerAnglePreview.LookAt(gravityTarget.position);
             oldZ -= playerAnglePreview.rotation.z;
             playerAnglePreview.Rotate(0,0,oldZ);
 
             Vector3 desiredRot = playerAnglePreview.rotation.eulerAngles;
             transform.rotation = Quaternion.Lerp(transform.rotation, Quaternion.Euler(desiredRot) ,Time.deltaTime * weightPower);
 
             // Note I also tried to make a look at using the position.z of this object but it dint work either..
 
 /*            dir = currentGravityText.text;
             Vector3 desiredRot = Vector3.zero;
             if (dir == "up")
             {
                 desiredRot = new Vector3(-90,0,oldZ);
             }
             else if (dir == "down")
             {
                 desiredRot = new Vector3(90,0,oldZ);
             }
             else if (dir == "left")
             {
                 desiredRot = new Vector3(0,-90,oldZ);
             }
             else if (dir == "right")
             {
                 desiredRot = new Vector3(0,90,oldZ);
             }
             else if (dir == "front")
             {
                 desiredRot = new Vector3(0,0,oldZ);
             }
             else if (dir == "back")
             {
                 desiredRot = new Vector3(0,180,oldZ);
             }
             transform.rotation = Quaternion.Lerp(transform.rotation, Quaternion.Euler(desiredRot) ,Time.deltaTime * weightPower);*/
 
             /*
             down = (90,0,oldZ);
             up = (-90,0,oldZ);
             back = (0,180,oldZ);
             front = (0,0,oldZ);
             left = (0,-90,oldZ);
             right = (0,90,oldZ);
             */
 

The part before the first comment is what gives the result you see in the Video , I am pretty much desperate at this point. I really need to be able to switch the directions the foot of the player look at WITHOUT changing the rotation from left to right,

I can change the gravity and walk on walls just fine as you can see but the camera makes the look at on all the 3 axis :(