Try this:

1. Open Firefox
2. Tap the menu button (three dots icon in upper right of screen)
3. Tap settings
4. Tap advanced
5. Tap restore tabs
6. Tap Don't Restore After Quitting Firefox

See if that does the trick.

Didn't help. I wanna keep all of my previous tabs. It's just that if I close a tab on purpose, close firefox, and open firwfox, that tab that I closed will be back, as if I never closed it.

Ah, I understand.

Did you download the Firefox app from the Google Play Store or sideload it? If so, is there an update available for it?

I downloaded it from the playstore. I'm just going to use a different browser... I may return to Firefox for android when they fix their browser!

I can confirm this behavior, and I'd be interested in a fix too.

Hey! I've deleted the Firefox's app data and reinstalled it. Appears to be working correctly now. (If I close a tab and immediately close firefox, then open it again, the tab stays closed!!

To get your desired behavior you can try a workaround:

   Type in about:config in the address bar and press enter.
   Bypass the warning (if shown).
   Find the entry "browser.tabs.closeWindowWithLastTab" using the search box and set its value to false. 

What it does is, it prevents the window from closing with the last tab. You'll have to close the window separately (one extra click). But there won't be any tab left to remember for the next browser launch.

None of these solutions work for me.

Have the same problem closing the Firefox tab is annoying tried deinstalled and run it again nope... Also blinks on app button icon it appears after the last update came... Getting more user unfriendly even though I use Firefox so many years since day one it's not working as it should be having more issues from update to update... Very annoying