Diễn đàn hỗ trợ Firefox

Hi there, I'm having trouble opening firefox that suddenly didn't open after I've used it as usual. When I've closed it, I've put the macbook on sleep mode and then reopen it after 10 minutes and tried to open firefox as always. It didn't. I'm trying to figure it out and I've followed all the possible paths on Mozzilla's support and others blogs, but none of them worked out. I've tried also to uninstall and re install firefox from scratch, but nothing happens: I still get the message. At this point I don't care if I need a fresh start, I have a bookmark's backups so, how can I really uninstall Firefox and install it from the beginning? Is there a hidden folder I'm missing? Thank you in advance

MacBookPro8,2 - macOS 10.11.6 El capitan

I need to have Firefox on my old Macbook pro, but its OS (10.11.6) will no longer update, and a new Firefox download won't take. Can I download an earlier compatible version?

All routes to access gmail accounts on Macbook air do not connect. If I type "gmail.com" as URL the bar reverts to "about:blank." If I open google and click on "gmail" or try to access through the apps grid the "G" icon flicks but I'm not taken to account. I can still access the base account through phone or chrome so the issue seems to be through this browser.