Problem when making extrusion on a 3d mesh

Hello everyone!
I’m working on a design and I’m experimenting the extrusion on 3D mesh.
The idea is to add thickness to the 3d mesh but when I’m trying to make a solid extrusion or offset I can’t control the direction and one way or the other the operation doesn’t work.
I have attached files below, can someone please help me and tell me what am I doing wrong or if it is a better to achieve the requested.

I have no clue where to go from here.

Best,1.013v (7.2 MB)

Please don’t double-post…