Start with the right checks.
A storage warning is a reason to check the contents, not install a cleanup advertisement. Establish which drive is full and whether the large items are personal files, applications or temporary data.
What to do next.
Open Settings, System, Storage and review the categories on the affected drive.
Copy important files to an approved recovery location and check that they open before removing local copies.
Review Storage Sense settings carefully. Its automatic cleanup choices can remove files, so do not enable options you do not understand.
Remove only clearly unnecessary items you own. Keep system folders and unfamiliar business application data intact.
Check the result.
Check the available space again and try the task that failed. Keep enough working space for normal updates and application activity rather than aiming only to remove the warning.
Stop and get help if…
The drive fills again quickly, the space totals look wrong or important files are the only large items. A technician can review retention, storage and application behavior without guessing what is disposable.