User permissions on admin area I created a new role, and this role should only have the permissions to insert/edit/remove to content types.

The problem is that the admin menu ( Navigation Menu ) doesn't show up in the admin area, and I can't seem to figure out why.

The other problem is that if I login with this user, and access the create node by putting admin/node/add ( since the Navigation menu doesn't show up ), I can create every content type available.

What am I doing wrong?
I think you should make use of proper permissions. If you are using Drupal7 , login in as admin and click on the people->permissions->content type-> add/edit/delete own contents. Once this option is enable and saved the user can modify only his content. I am not clear with your question, it would be glad if you make your question more precise.