How do I adjust the timeline to eliminate seconds of silent space in preview/publishing mode

I work as a subcontractor to the government , I am unable to share the storyline that I am working on due to the circumstances What I am doing and trying to do is.

I have one slide that contain  7 audio clip[s. I also have 7 buttons and 7 place holder on this slide. I also have 7 layers connected to the slide .

! layer per audio clip, 1 button and 1 placeholder per audio clip. The button and placeholder are connected .I want the user to have to hit each button, listen to the audio clip and once the audio clip has ended the user gets back to the slide with the 7 buttons. I want each button that is connected to the audio clip to turn color when the timeline ends this will help the user to keep track of the audio clips listened to. Once the user has listened to all 7 audio clips the button that takes them to the next slide will be activated. I would also want the user not to be able to manipulate the audio clips in order to speed through.

I have managed to make sure the user gets back to the slide with the buttons once the audio clip is ended. I have 2 issues, the state does not change for one at a time but for multiple, depending on which audio clip button it is not even part of the ones that change state. I do not have any basic formal training on Storyline but had to jump in the pool on the deep end and figure it out. My second issue is that in each Layer depending on which Allow seeking setting I choose the audio ends without any silent space but does not change color or extra dead space is added and the color changes. I hope you understand what I mean and what I am trying to explain.