iCloud

I use iCloud on different device ( 1 macbook, 1 iPad and 1 iPhone) and sometimes it takes ages for FILES to sync. It's like a black box. I don't understand how often iCloud syncs nor when. Also, no clue if and how I can force a synchronization or if I can change settings for more frequent syncs.

Since I use iCloud for business purposes this really annoys me and solutions (for forced synchronization and settings) would be greatly appreciated!