I seem not to totally understand the group permissions. I hope someone can help me out.

1. Post comments - clear
2. Front-End Editing - clear (thats a preset for everything, right? otherwise everything following is useless)
3. Add items - clear
4. Edit own items - After pressing send where is the Item? If its not published its also not accessible...so i don't really get this option. What's the point of having to publish something that needs editing?
5. Edit any item - which items? Again the items already published? Sorry i don't understand how this can be useful. If i don't see unpublished items, why should i edit anything? I can't publish my artices before they are corrected.
6. Publish items - clear (altough this option is nonsense because default is "published")
7. Allow editing of already published items - ?

If i put 7 to "no" what impact does that have? Does it mean i can't edit anything anymore because i can't see unpublished items anyway?

I am really sorry but it seems i don't really understand the system. It doesn't fit to such a great extension.

The Edit own items means that a user can edit only his items (the ones he is an author to)
The Edit any item means that a use can edit all items even the ones he hasn't authored.
The Allow editing of already published items does exactly what it says. If you set it to know you won't be able to edit the published items from the frontend. The unpublished items can be seen in the user's page.