Help really needed

I think what you are asking for can be 'split into two'

  1. You want your site to show a thumb-image. This will require the Content to have an 'image' field. The File content types do not have an image field. So you need to add the image field.
  2. Adding the Image field can be done:
    manually, with for example: https://plone.org/products/content-lead-image
    You will then have to take a screenshot of each file when you open it in your Desktop program, and add this to the file.

.... or you can let Plone do this for you (which is a more complicated setup (?) with.

You might also want to take a look at: https://plone.org/products/document-viewer

PS: Take a backup before you start installing 'new things to your site'

Hello,

I solved my problem using another portal_type. It contains a title, an image and several files. I had one called "noticias" and on the portal_type and I made a copy/paste and create a new one called "newsletters", its a copy of the "noticias".

I can create and show everything with the noticias but not with the newsletters.

When add a new "newsletters" its ok but when I try to save it I've the following error:

Here is the full error message:
Mostrar o traceback como texto
Traceback (innermost last):
Module ZPublisher.Publish, line 126, in publish Module ZPublisher.mapply, line 77, in mapply Module ZPublisher.Publish, line 46, in call_object Module Products.CMFPlone.FactoryTool, line 453, in call Module ZPublisher.mapply, line 77, in mapply Module ZPublisher.Publish, line 46, in call_object Module Products.CMFFormController.ControllerPageTemplate, line 75, in call Module Products.CMFFormController.BaseControllerPageTemplate, line 28, in _call Module Products.CMFFormController.ControllerBase, line 231, in getNext Module Products.CMFFormController.Actions.TraverseTo, line 38, in call Module ZPublisher.mapply, line 77, in mapply Module ZPublisher.Publish, line 46, in call_object Module Products.CMFFormController.ControllerPythonScript, line 161, in call Module Shared.DC.Scripts.Bindings, line 322, in call Module Shared.DC.Scripts.Bindings, line 359, in _bindAndExec Module Products.PythonScripts.PythonScript, line 344, in _exec Module script, line 4, in noticia_edit
<ControllerPythonScript at /Site_isptec/pt/noticia_edit used for /Site_isptec/pt/newsletter/portal_factory/Newsletters/newsletters.2016-04-19.8231864918>
Line 4 Module Products.CMFPlone.FactoryTool, line 301, in doCreate
AttributeError: 'builtin_function_or_method' object has no attribute 'strip'

ps: the initial view name and default I only switch the name, didn't really create anything