I tried restoring a backup I created from my iPhone (it had more than 20Gb free out of 64Gb) but when I wanted to restore this backup I found out the backup iTunes created was 61.5Gb, so whenever I try restoring it says not enough storage. Any way I could restore data still? I know I have 22Gb of photos, if it could help. I have tried to factory reset my phone so I can choose the "restore from itunes backup" option, and still I had the same problem.
That backup is awfully larger than it should be. I dont think you'll be able to restore it on that size, you'll need a 128GB model for the update to work since most OS sizes are between 8GB - 4GB of that base memory. Thats why you are having problems.