If the media on the timeline is a PowerPoint, was it a video that was recorded as the slide show was playing? Or was it imported?
If it was imported, you are most likely working with a simple image. If that's the case, you simply need to adjust the duration of the image. And that may involve moving other media that follows "down the track". To do that, select the next image, press and hold the Shift key, then drag to the right and all of them should move. Adjust the duration as desired, then repeat the process by clicking the next media to the right, press and hold the Shift key as you drag it back to touch the media you just extended.