iMovie not uploading to my camera roll
I am 13 years old and I have just made a new YouTube video and edited it nicely in iMovie. It is 13 minutes and when I try and save it to camera roll it stops near the end. I tried saving a short video to my camera roll and it worked. I am doing it on 720 p but i don't think it's the quality- the upload bar just stops near the end. I've researched loads and can't figure it out and have tried adding a photo to start( a solution on YouTube) but nothing happens. PLEASE HELP thank you.