I'm not sure how much I can help, but I have recently (repeatedly) downloaded and installed Firebird to my Linux installs. I'll let you know what worked for me.
First, my /home partition is about 5GB. I thought this was necessary in order to make sure I had plenty of room to store downloads, data files and whatever else I decide to put there.
Second, I created a /home/common directory and set the permissions as drwxrwxrwx to make sure that this was truly a "common" directory for everyone who uses this system. Then, I downloaded the zipped file into a /firebird subdirectory of this common directory. I used "file roller", I believe, to unarchive the files to /usr/local/firebird. My /usr partition is around 5GB, also, so I can install a lot of fun
Linux programs. Then I went to my taskbar, right-clicked, clicked on "Add to panel" and selected "Launcher". Then I clicked the "Browse" button, navigated to /usr/local/firebird and clicked on "MozillaFirebird". I changed the icon to the one in the firebird/icons subdirectory and began browsing at my pleasure.
It's really about that simple. But it took me a couple of times to get that figured out. This is truly a very uncomplicated OS if you just keep it simple and do a little reading and planning before install (which I did after about half-a-dozen installs).