Remove (or reduce) background music, and emphasise the background voice
You already tried EQ unsuccessfully, but there is one more technique worth trying:
Add the original music again to the soundtrack, but with inverted samples. This will cancel out signals. For a bit more theory, check out Wikipedia and the graphics on the top right which illustrates what will happen. The success depends on the mix and applied effects in the video soundtrack.
The basic steps are as follows:

Import soundtrack and import the original music on a separate track (probably that are pairs of stereo tracks)
Sync/align the music track so it matches exactly the music soundstrack. Be aware that the music in the video could have been slowed down or sped up a little bit. Apply the change speed effect on the imported music in this case to make it match.
Try to match the levels of the music track to the music of the video track for best results. Not sure if this can be done automatically in Audacity. Look for a short section on the video track where nobody's talking and compare levels there.
Invert the audio. More on Audacity's invert here.
Mix the track with inverted music to the video soundtrack. (Since both will probably stereo you can try multiple combinations, either add the inverted left to soundtrack left and inverted right to soundtrack right. Or switch them.) I don't know Audacity well enough to tell you how the mixing works. I only ever used it sporadically many years ago.
Music will cancel out or be removed to some degree.

The problem is: if they have applied any effects on the music in the video soundtrack the cancellation may not work well.