There isn't any audio on the video i generated with prompt, also how to increase length of video to tell complete story

I have generated a video with descriptive prompt where A leader is narrating her story where her experiment failed but she got some learning to do better, the challenges I have with the outcome of video are .1. No audio at all in video and 2. the entire script is not converted in to video it is just created for 8 secs, how to increase the length and have entire story narrated