[solved] 9:16 videos in iMovie

I wanted to edit a video in 9:16 format in iMovie but the exported video was always in 16:9 format with the corresponding large black areas to the right and left of the video.

in iMovie go to choose File
then select: new App Preview
first video in the timeline must be 9:16

I hope this has helped you. If you have any updates or additions to the problem, please let me know.