Hello Mike and welcome to LinuxQuestions.org.
if I df I get that /dev/hdb1 100% in use. Is this how it is supposed to be?
This is possible. What this is telling you is that your hard drive is completely full. In order to make room on your hard drive you will need to delete some files.
I cant figure out what I can delete and not delete.
This is a tough question to answer. If you are new to linux then I would suggest that you navigate to the home directory, which is located at:
Then from the command line issue the command
This will give you a list of all the directories and their sizes. Pick the largest directory and navigate to it. You can continue to use the du -h command to help you find the largest directories within other directories.
Once you have navigated into a large directory you can use the command:
to find the largest files in that directory. Doing this you may find that you have some large files on your computer. You can start deleting files that are large and unnecessary, for example a sound or movie file, but if you do not know what the file is or what it does then I would suggest you NOT delete it.
If you would like to get more information on a file from the command line then you can issue the command:
where <file_name> is the name of the file you want to know more about.
Good luck and I hope this helps.