size of letters too small, also want Hebrew, also why no files on desktop? Thank you

Yes you can save files onto the desktop, it's just like saving to any other folder, (when your saving something you just navigate to the desktop folder and hit save, then it will be on your desktop) To get larger fonts open up the ubuntu software center and search advanced settings, once it is installed open it up and click the fonts tab in the side, then there should be a bar you can drag to change the size. For hebrew open up language support, (it may say something about not being fully installed (just hit ok, this installs languages onto your system)), you then should be able to select hebrew from the list of languages, and set it as the language, hope this helps.

1. See here
http://askubuntu.com/questions/19770/how-do-i-change-fonts-and-adjust-their-size

2. Can you be more specific here. Do you just want to be able to create and edit Hebrew documents in libre office?
if so see below or more generally?
http://opensiddur.org/2012/04/how-to-work-with-hebrew-in-libreoffice/

3. Yes the desktop is blank when you first install Ubuntu but you can put files there its just a folder in your home directory