Hi HatziGr, I am Paulo and I'd like to help.
Have you tried unpinning all desktop icons and then restoring them to default? Go to Settings > Personalization > Themes > Desktop icon settings. Uncheck all icons then hit Apply. Once done, click on Restore Default and then select back the icons.
If that didn't work, try to clear the thumbnail cache
https://www.elevenforum.com/t/clear-and-reset-t...
and rebuild the icon cache using option two in the methods below
https://www.elevenforum.com/t/rebuild-icon-cach...
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