Hi

It is not possible to downgrade Firefox for Android and go back to the previous user interface.

Thank you; that does not solve my problem, of course, but it is a fast and to-the-point-answer. I will look out if the missing items come back. As FF is now I have difficulties to see why it is worth installing it. Its look and use are very similar or nearly identical to the standardbrowser on Android, and using the latter will save me space on the device (because it is installed anyway). Untill now, FF had a superior interface, but with that gone?

You can downgrade by uninstalling the app and reinstalling a previous version from an APK mirror. This has some major caveats, though.

• It's your own responsibiltiy to determine if the source is trustworthy. It's not unheard of for websites to provide manipulated APKs that have been injected with malware. There are, however, several APK mirror websites that are known to be trustworthy and offer original, unmodified APK files as they were distributed on Google Play Store. (It's always safer to back up APKs yourself directly from your phone, but unless you're going to do this regularly for all apps you use, you're probably not going to have this since you don't usually expect an app to get broken).
• You have to enable the option to install apps from untrusted sourced in your device settings, which also can have security implications.
• The version you'll install will be no longer officially maintained or updated, including security updates. So you'd probably only want to do this as a stopgap solution until the problems you're having with the current version are fixed.

I do this regularly for many apps who were broken in an update (although, to be fair, usually for way less critical apps than a browser). In fact, I think the inability to access previous versions directly is a major oversight in the Play Store and really ought to be offered officially. But at least, in contrast to iOS, Android users have the option of this manual workaround.