To completely remove Grammarly.app and disable its features, follow these steps:
Go to your browser's extensions/settings menu
Find Grammarly extension and click “Remove” button
Go to your computer's control panel and search for Grammarly in the installed programs list
Click “Uninstall” to remove Grammarly from your computer
Restart your browser and computer to ensure the changes take effect
Check your browser settings to ensure that Grammarly is no longer an installed extension
If you continue to see the pop-up floating command thingy or overpowering grammar options, you may need to clear your cache and cookies to remove any residual data.
Once you have completed these steps, you should no longer see any Grammarly-related features or pop-ups on your computer.