Mirror Modifier creates the other part of model far away from the original I'm doing a girl here (the concept is not mine, I'm just training) and when I click on mirror modifier Blender creates the other part of the model far away from the first one, not close like it should



I have no idea how to change that, does someone know what is the reason it works that way?
The Mirror modifier works exactly "as it should".

Meaning it will mirror the geometry using the object's origin (that orange dot that you see in the girl's forehead) as the axis of symmetry. If your geometry is far away from the origin, the mirrored geometry will be as far away from the origin but on the other side of the axis.



Read the blender manual page to understand how the tool works:
https://docs.blender.org/manual/en/dev/modeling/modifiers/generate/mirror.html?highlight=mirror%20modifier

As an alternative to using the objecct's origin, the mirror modifier can also be used with a control object. As detailed in this answer: https://blender.stackexchange.com/a/49355/1853