No, I don't think you need to.Do I need to make another directory and put the firefox directory in the new directory?
Yes, because I noticed file roller created a folder, then extracted the contents into that one. That screenshot of firefox.desktop is the one you're using? Cause I see Exec=/usr/bin/firefox. And for the name, I see Firefox Browser.You have /opt/firefox/firefox/firefox in the argument in the Desktop Entry like this: