How can I set a picture which I have taken with the camera and set it as my background. I only got my 3650 today. Thanks.

In the "Tools" menu there's a "Settings" app; there go to "Standby mode" > "Background image" > "Yes" > select your picture.

Read also the phone's User's Guide for more things you can do (this particular thing is also stated there; page 28 in the English language version).

This book might also be useful to you: http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0764579428.html

Thanks for the help.