I understand you very much since I have a similar problem quite often. The fact is that I am a beginner photographer, and the memory on my phone will fill up very quickly because of this. However, I can advise you of a life hack suggested to me by someone from YouTube how to make a video a live photo https://backlightblog.com/live-photo-to-video-or-gif. It was a salvation for me since I saved the essential frames from the video and deleted the rest, thereby freeing up space on the phone. Try this life hack, and maybe you will look differently at the organization of storage of your files in the iPhone. Good luck and I hope you resolved your problem as soon as possible.