My WAV files are not modifed after saving

Hello, I use Audacity from a year ago, and this didn´t happen never.
I modify the audio WAV file so that it matches the values I want. Then I save it in WAV also. Then I open the saved file and DO NOT HAVE THE SAVED VALUES! This never happened to me! I have always do the same thing in the same way. I save the file with some values, reopen it and have VERY DIFFERENT values
What is happening? What can I do? I insist, it never happened to me, I always do the same exact process.

I have tried some methods, and for some files it works but not anymore, I cant understand anything!
I convert the MP3 file in WAV file.
I work on the WAV file to match the values.
I save it as MP3.
I open MP3 file and matches values, so I save in WAV.
Problem solved!
BUT! That method only worked for 2 files!!! Not anymore.

I attach the images

  1. The values in MP3 original file as I want. I save it in MP3 and WAV
  2. The WAV file saved with OTHER values
  3. The same WAV file after adjusting, saving in a new file and open it, again with OTHER VALUES

Thank you very much for your help