How Do I Remove A Narration From A Movie?

Hi there :) I have a movie file on my computer that I really like and want to watch, but the problem is, is that someone has added a narration over the English audio,(which is still present, but very hard to hear because of the implemented narration), in their native language. Now I know that there's a lot of posts and forums about how to add your own narration, but very little info exists on how to remove them....especially if it is someone unknown to you who added it. Any help so I can fix this would be greatly appreciated. :)

PS: The movie is called "Bridge to Nowhere" made in 1986. It's a very hard movie to find on DVD/BluRay.