how can i recover a file i deleted

From your Time Machine backups, most commonly.

Restore items backed up with Time Machine on Mac - Apple Support

If you do not have Time Machine (or some other backup) going, go get that configured and running.

Back up your Mac with Time Machine - Apple Support

Or if the file was stored using iCloud: Recover deleted files on iCloud.com - Apple Support

It's probably still in the Trash. Right click or control click on it and Put Back in that menu.