Sync audio (How to reflect media changes in timeline)

Hello,

After editing all the footage I realized I made a mistake, forgot to sync my external audio with the video! (I would have learned to never start a project with little time and not focused...)

There is a way to sort of update the timeline so that it recognises the video with two audio in it?

Thanks!

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EDIT

My bad, actually that part works, but I can't change the audio attributes and add an audio track in timeline (see screenshot)