My /dev/sda4 disk space is full. I have allocated 70GB, I don't think it is full. I tried to fix the problem but don't know how to resolve this
Solution 1:
You do not think it is full. However, it is full as indicated by the output of df.
A root space that is full is problematic and can cause your system increasingly malfunction. Move as quickly as possible some user data to another drive to create space again. Make sure your root partition never is filled more than 80%.