hi does anyone know how to make a childObject only follow the position of the parent but not the rotation?
You could always store the rotation (euler angles) of the child before the parent moves, then reapply the stored rotation afterward, (probably in LateUpdate).
Alternatively, you could have the object not a child of the parent object at all, and just find the difference the "parent" has changed in position every frame, then move the "child" by that much.