1

How cam I make a gameobject inside a camera stay always in the same position when the camera moves.

Please someone answer.

2

You can drag a GameObject onto another GameObject in the Object Hierarchy tab to make it a child object.

3

You can parent in the Hierarchy, or you could have a look at transform.parent. To match positions, you could just use something like:

transform.position = Camera.main.transform.position;

Then parent:

transform.parent = Camera.main.transform;