I need to unlink the audio track from the video track in Expert mode.

Hello, my first post here about a question that seems so basic to me but I spent several frustrating hours yesterday trying to accomplish this. I have made several videos in the past using different software on a PC but this is my first video using Elements 2020 on my iMac. 

The audio track is basically a song in mp3 format imported to the music track or audio track (I've tried both!) I'm trying to edit still photos and some inserted video into the video 1 track and changes I make there cause the audio track to break apart. Also, if I change the duration in any photo (except the last one) it also creates an unclosable gap in the audio track. I need to be able to work in these tracks independantly to create my slideshow. When I have everything in both tracks selected and right mouse click the option to ungroup audio and video is not active. How can I unlink these two tracks in Expert mode for the entire timeline? Thank you for any advice ...