How do I copy a finilized DVD to my computer using DVDfab? Or any other program?

I have a finilized dvd of a show I performed in but the sound is horrible, the volume I mean, very quiet. Im trying to rip the dvd to my computer using dvdfab so that I can edit the movie, insert chapters, and also make the volume of the audio louder. The only problem is that when I rip the dvd to my computer, the audio and video does not sync up, and the video is playing faster than real time. I have also tried using an older version of dvdfab and its the same.