Anyone with Fire and CM12 installed on it- can you run firefox?

hi,
I have a fire (2015 ) and CM12.1 (taken from this forum).
I'm trying to install firefox.apk and firefox-beta.apk taken from the google playstore but it keeps telling me "app not installed".
I'm tearing my hair over this and have already tried many things and wasted many days but it only now occurred to me that it might just be a problem with CM or the Fire tablet (or their combination).
If any one could please try and install those two apps and tell me of the results (and of what version ROM/device they have) that would be great!

https://play.google.com/store/apps/d...ozilla.firefox
https://play.google.com/store/apps/d...a.firefox_beta


Thank you very much.

Problem exporting Firefox bookmarks on desktop to Firefox on mobile device

Hi, I'd like to use my Firefox bookmarks from my desktop on my Nexus 7. I can export them to a bookmarks.html file and adb push that file into the /sdcard/Download folder on my Nexus 7. But there Firefox can't read this file, it just shows me a blank page. No error message.:mad:
My Rom is a Cyanogenmod 13 snapshot from 2016-04-18 and the Nexus 7 is the "deb" version with LTE. And it is rooted.
Do I have to modify the file permissions, and how canI do that? The CM filemanager shows no option to do that, and the "chmod" command won't work.
And I wand avoid creating another online account (Firefox Sync) only for doing that.

Greetings,
Heinz