How to reinstall unity desktop on Ubuntu 14.04 [duplicate]
Type the following in a Terminal:
sudo apt-get update
sudo apt-get install ubuntu-desktop
Now reboot and you should have the Unity desktop environment installed.
For dependencies after installing something else try
sudo apt-get check
sudo apt-get install -f
It should repair all problems with dependencies or errors
Edit:
Check this link about installing multiple environments
Check this AskUbuntu either, maybe it could help you