Automatic Backup issues

Hello all,
I have major issues with Auto Back up function. I wanted to automatically back up my photos/videos from my Iphone 12. When i turned the function on first time, it created a Iphone camera roll folder on the MyCloud drive and started to download it all (or so i thought). Today, i changed the name for my iphone (now called my12Pro), this created automatically a new folder (and keeping the old one) on the drive and he started to download again. Then i looked at it curiously. This new folder has 5,887 items for 84.81GB. The old one has 2.840 items for 48.23 GB. On the Iphone itself, the photos app takes 106.8GB of storage ??? i can not make sense of any of it, why a new folder, why different size and how do i know i have all backed up ??**