My simple questions: Is the community edition version 5 able to work together with the mobile app for the iPhone or not? If yes: Is together with the community edition version 5 the transmission of the password as well as the transmission of the content encrypted or not?
Yes, Alfresco 5.x Community Edition does work with both the latest iOS and Android mobile apps.
Transmission of the password (and all other data) depends on whether you are accessing the server via HTTPS. If you've setup SSL/TLS on your server and you have configured the mobile apps to connect using HTTPS, then yes, all traffic will be encrypted.