Windows is not static in size. The System Restore feature keeps a copy of what changes happen on app installs and updates. No one will advise you turn this off.
However as a test you can turn it off and see if space returns. (How to is on the web so I pause here.)
For the past month my laptop has been losing 1 gb every day or two. I have lost almost 20 gb so far for no reason. I have not downloaded anything, either. I have performed a scan, Malwarebytes, for malware. No malware was detected. I also cleaned my disk with Wise Cleaner. What can I do to stop losing disk space?