Having listened to both clips, I have two things to share:
1. The first audio track (Audio track.7z) is actually fairly decent. I've heard far worse.
2. It's been compressed pretty tightly, and is somewhere between the second clip (Audio Sample.7z) and telephone quality. I can only guess that noise has been removed. Noise often masks/replaces legitimate audio, and when the noise is removed, you have a reduced quality audio file. At most, you can tweak EQ values, to attempt to give a false tonal balance. But it sounds like that was already done.
Nothing will ever make the compressed (data missing) version sound like the unmolested original.