all my faces are 3d what happened?

Could it be that you weren’t in Wireframe Mode when you selected (maybe with Box Select), what looked like all the Faces:

but that way you only selected the ‘front’/visible Faces and whebn you then moved them, some were left behind:

I have done this sooo often and sometimes it still happens to me 😉 When I’m in luck I notice it immediately, but sometimes….

The opposite also happens: there is something (out of view) still selected when you move some part of your mesh and that gets moved with it unintentionally.

You asked what happened 😉

To revert use Undo (CTRL+Z) a few times. If that doesn’t take you back far enough:

Go to Front View and with Vertex Select  and in Wireframe Mode select one half and delete it and the select the rest and extrude on X-axis.

Can’t see what your X Mirror is doing though, but the trick should work anyway, just don’t delete the ‘mirror-line’ vertices.