Hello. My name is***** can help you with your question.
If you go to the properties panel of the slide, you can set the duration for which it will display. If it is showing all of your slides, but they are ending before the music is finished, then this is what you will want to adjust.
Use to change the duration for which the slide plays. The maximum value is 1 hour (3600 seconds).
Set those for the times that you need. If this does not correct the problem or have other questions, please let me know.