Deleted almost everything from MacBook Air (2014) and still no storage?
Reinstall macOS

It looks like cached system files are what's causing your storage problem. Reinstalling macOS will not delete any personal information or files, but resets all system files and restored deleted system apps.

here's what Apple says about reinstalling macOS. I've reformatted the directions below to make your life easier:

Start by pressing the appropriate key combination for what you need. I suggest Command-R:


Now, using macOS utilities, select Reinstall macOS:



Simply wait until the download and install is complete and your cached files should be cleared, solving your problem.