How do I delete an app?

Boot into Safe Mode according to How to use safe mode on your Mac and delete from there.

Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.

Exactly which app are you trying to delete?

Apple apps included and installed with macOS cannot be deleted.

Generally speaking, quit the app. Then find the app - usually in the Applications folder - and drag it to the trash. Then empty the trash.

Otherwise, restart the Mac and try again.

Depending on the app, you may wish to visit the publisher website for an uninstaller tool and guidance.

Please visit:

Citrix.com/support

Also: https://docs.citrix.com/en-us/citrix-workspace-app-for-mac/install-uninstall.html