Now my ubuntu shows the loading screen and doesn't load any further. I made a live cd and booted from it but I can't explore the needed files. I read that the partition with the installation has to be mounted but I'm not sure. Please help because my information is very important to me. 10x in advance.
First of all find out which partition you have your data on. For doing this, you can boot into live, type in "sudo fdisk -l" which will show you all your partitions, try mounting them one by one till you find out which partition has your data, and once you have found out that partition, you can copy tour data from there.