Could someone give some tips or check simple class diagram for mobile application?

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I'm working on preparing a class diagram for mobile application. The application is meant to be something like a diary from journeys. Here are the requirements:

  1. One user can create many trips.
  2. One trip can be to one or more places (destinations, cities).
  3. There might be assigned many albums with pictures to each trip, categorised in custom way, for example one album is for food pictures, one is for people user met during a trip etc.
  4. Each picture can (but doesn't have to) have a description.
  5. User can add contacts to a contact book.

I have created a very simple UML class diagram using StarUML. I am not sure if it all is correct, maybe there should be some association class used instead of something or maybe different kinds of relationships.

Could someone please check it and maybe give some tips and corrections?