The game doesn't delete old autosaves. In my case it got to the point of over 200 MB of save files and so the synchronisation to the cloud save service of GOG doesn't work anymore. I get the error message that I have to delete old save files first. But even when I do so, it loads them back from the cloud backup when I start the game again and I get the error message again. So I disabled cloud saving for this title.

I hope this will be fixed in an upcoming patch.

I've started a new game, so that the old autosaves and the old mission starting points got deleted under "C:\Users\username\AppData\Local\Terminator\Saved\SaveGames".
But when I start the game GOG Galaxy still does synch all the old autosaves (from 0 to 280) that where in the folder "C:\Users\username\AppData\Local\Terminator\Saved\SaveGames\Backup", even when I delete them manally. The next time I start the game, I have to wait until this old and unwanted files get downloaded again. I finally deactivated cloud synch for this game.


Nevermind. I've found the solution in this other thread:
https://www.gog.com/forum/general/how_to_delete_cloud_saves