So the other day I wanted to upgrade Ubuntu but my laptop lost internet connection half-way, and now Ubuntu is only half-upgraded and I can't access anything anymore... I can't reconnect to the internet as this function is not there anymore (due to the half-upgrade I guess), and when trying to click on anything or search for anything nothing happens... Do I have to set it up again fully now? And if so, how can I save all my data and stuff?
If you can't connect to the internet because the function is missing, you will most likely have to re-install Ubuntu. That said, backing up your data is easy as Ubuntu install discs have a live session you can use to access files on the computer.
Just boot up the install disc (I recommend the 13.10 release, so you don't have to upgrade again) and choose Try Ubuntu. Let it complete loading and you can now navigate through all your files. Just plug-in a USB drive with enough space on it, and copy all the stuff you need to the new drive. Safely remove the drive and start your installation.
PS: Next time, be sure to upgrade when power is connected, internet is stable and you have the time for it to complete.