The textareas of the items are not showing in the admin page under "Manage listings" like its showing in the item.php (images are attached).

In the admin page only the Job position title and Position details are showing. The other ones are not showing at all!

@developGr
I would recommend to select a category first when adding new listing from backoffice, I would say you have tried that 

I have tried that, selecting category first but still nothing!

@developGr
Than you have some javascript errors on your site.
It works properly on demo.

i have some "Custom fields" that after i select a category are shown just fine under the "Add new photo" (screenshots attached) but the 1. Benefits & Bonuses 2. Selection process 3. Required education 4. Qualification and skills 5. Language are not showing!

 2nd screenshot

@developGr
I see it there on screenshots.

The fields under the "insert image" its the "Custom fields".

This is what it looks when the user add listing not from admin but from "item-post.php"

and 3rd screenshot

as you can see the "Custom fields" are showing under the button "Click to upload image"

In the admin page "Add Listing" those boxes: (screenshot attached) are not displaying