Hi there @Antaris98 very sorry to hear you're having some trouble with your auto-saves and manual saves.
There's a few things that can cause this issue, so I will provide a few articles to guide you through some fixes.
First, if Ubisoft Connect does not have administrator rights, it can prevent saves from being made properly. Start by Reinstalling It by following these instructions.
After that, you will need to make sure Ubisoft Connect is always running with Administrator Rights.
Finally, Ubisoft Connect and the game files need to both be installed onto the same hard drive, if you have multiple drives in your computer. If you do, please make sure that both are on the same hard drive as your Windows installation if possible.
Let me know if you keep having trouble with your saves after this. If you are seeing a specific error message in-game when the game attempts to make an autosave please take a screenshot of that as well.