Fixing out of sync video on Youtube

I am unsure where to put this. I downloaded my friend's video on youtube and got the video file. I cannot seem to separate the audio track from the video track. The video is extremely out of sync in several portions. It was an online concert. They tried to to fix the problem during the live concert but failed so the video was syncing in and out as well as literally going in and out. Could someone help me with this problem?

To seperate video and audio streams, drop it into kdenlive's Project Tree, select the video, RMB menu 'Extract Audio To Wav' is one way or drop the clip onto the timeline and RMB 'Split Audio' or select clip in Project Tree and then go to 'Clip' menu above and 'Split Audio' etc