I’d suggest that you first look at your configuration like @Manuel suggested:
someuser@somehost:~$ cat /etc/default/keyboard
XKBLAYOUT="de"
BACKSPACE="guess"
XKBVARIANT="qwerty"
XKBMODEL="pc105"
XKBOPTIONS="compose:caps"
What does your file contain?
If you do not have the configuration right (for whatever reason) there is no sense in starting to modify single keys of a possibly wrong layout.