Slideshow on phone

Trying to make a slideshow for graduation on my phone. If I use the basic photos slideshow I can only select one song for music (tries making a playlist but still makes you check individual song). As soon as you check one song it goes back to main page.

so I tried iMovie app. It lets you select multiple songs but every photo I used in it that was vertical was cropped so that you can’t see the whole picture in the slide show (landscape pics worked fine). There are YouTube videos on formatting every vertical pic to 16:9 but this seems very complicated! Any ideas on either of these issues? Is there a better app to use?