How to export pcbnew file from gerber file

I’m trying to export pcbnew files out of gerber files but it seems it is not working properly.
Let me explain,
I have a gerber file that I’d like to edit its pcb (pcb file is not available).
Although the design in gerberview seems ok, when I’m exporting to pcbnew the design is completely different. Size of traces is lost (there are lines only as drawings), no filled zones etc.
Am I doing something wrong? I’ve also tried it with a pcb that was designed exclusively in Kicad.

Any thoughts?

Thank you for your quick reply Andy_P.