Who can help me, I have such a problem. How can I edit a video in iMovie and save the portrait without cropping iMovie into a square? Thank you very much for any answer

Hello everyone, I recently encountered the problem of inserting sound into captured videos on an iPhone. I did not understand how it all works since I have been using android all my life. Friends, too, did not help to figure it out since they had never done this. In short, I had to surf the Internet myself on sites on this topic. I found a good article where everything is described in detail, and only then I figured out this whole topic. By the way, I even make money on this, as I make videos for Instagram bloggers. In general, I strongly advise you to visit site that helped me, since everything is explained there. Good luck to everyone, guys.