audio editing in moviemaker

I am trying to create a movie using old video footage. I have added music and trying to mix where the vido sound should be louder and where the music. The tools are available and I did it too, but when I save the project it goes back to what the start point was and loses all the changes I made. Any fix for that?

Also, I am trying to use a certain part of the music, cutting a section from the mp4 I attached to the video, but I cannot edit the music. Is that possible?

thanks