high pass filter ... go back

i applicate the high pass filter 6db
two time
and save

my song is very too much deaf

how can i make the reverse operation after save :wink:
or what effect can offset this operation

Do you have a backup of the original unprocessed recording?

If not, you may be able to make some improvement by boosting the high frequencies with the Equalization effect (http://manual.audacityteam.org/o/man/equalization.html), but really you would be better to make a new copy of your backup file and start again.