Hi Pika. I'm Greg, an installation specialist, 10 years Windows MVP, and Volunteer Moderator here to help you.
In the screenshot you posted, click the link below Memory tab to Open Resource Monitor, on that Memory tab check how RAM is apportioned to hardware to see what's using it.
Test the RAM overnight to stress it with the best bootable test memtest86, following this guide to test both sticks and slots:
https://www.wikihow.com/Test-PC-RAM-with-MemTest86
https://superuser.com/questions/949244/windows-...
https://www.partitionwizard.com/partitionmagic/...
Run Crucial System Scanner to check the RAM is properly spec'd and configured: https://www.crucial.com/usa/en/systemscanner?cm...
See also these fixes for high RAM usage to check for problems:
https://fossbytes.com/how-to-fix-high-ram-and-c...
I hope this helps. Feel free to ask back any questions and keep me posted. I will keep working with you until it's resolved.
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