[Bret Thomas]

There is a manual below or if you no idea how to repair illustrator files for illustrator, when learn next:

https://helpx.adobe.com/illustrator/how-to/recover-files.html
https://smallbusiness.chron.com/recover-work-illustrator-39270.html
https://illustrator.recoverytoolbox.com/

1. Close Adobe Illustrator.
2. Right-click on the Windows “Start” button, and click “Open Windows Explorer, then the file manager opens. Navigate to the AI file to delete.
3. Right-click on the AI file to show the context menu.
4. Click the “Properties” option. The Properties dialog box opens.
5. Uncheck (clear) the checkbox next to the “Read Only” option in the File Attributes section.
6. Click “OK,” and close the Properties dialog box.
7. Right-click on the AI file, and click “Delete” from the context menu. Click “OK” to confirm the deletion. The AI file is deleted.