I was playing Deus Ex: Mankind Divided a couple of months ago.
Using GOG Galaxy to unlock the achievements.
I recently reinstalled the game and when I synced the data in the cloud, only half of my progress was downloaded.
I decided to delete the game saves and start over from scratch.
But every time I open the game from GOG Galaxy, it always downloads the same files.
I delete them inside the game, but all the time the same files are downloaded.
There are no options either on the website or in the client to delete the cloud save.

This sucks.

Ohh! Thank you.

No problem.

It's sort of/kind of hidden. They plan to limit cloud save space (200MB per game) and while they're sending notification emails with the link, they haven't put it anywhere in our accounts from what I know.

https://support.gog.com/hc/en-us/articles/18730340487709-Review-your-Cloud-Saves-to-avoid-loss-of-files

I guess the reason why half of my saved data disappeared is due to the new limitation of cloud saving.

Hm. Hard to tell, the support article says August 31st.

Out of curiosity I clicked that link.

I never downloaded/used Galaxy.

So - technically, GOG shouldn't show me anything - instead, it warns me:

"[warning sign] Action Required
Your cloud save files that exceed the default allocation limit (200 MB per game) will be deleted after August 31st. Review them and delete any unnecessary files or old saves, to avoid loss of the important files stored within your cloud saves."

This is so GOG... XD

Everybody gets to see the message. Better safe than sorry I suspect. ;) (Or, alternatively, they didn't think it's worth the effort to make it depend on whether you created any cloud saves or not)