how to delete sync photos from my iphone 5S?

Hi all,

my iPhone is out of storage so I'm trying to "delete" some of the sync photos.

i tried so many things like remove the pics from "my picture" to different location, or create a new folder and with 1 picture and set it up as the new sync folder but no matter what i do, i always get an error when i'm trying to apply the changes on iTune that the sync can't be done because there is no enough space on my device.

This is one of the manual i followed but it didn't helped: Delete photos and video synced from iTunes when you can’t access the originals - Apple Support

I'm trying just to delete pictures and not to add anything else so i don't understand why I'm getting this error and how to free my storage.

please help.

Thanks