Hi  !
Is   'Elasticsearch'  your search engine by choice   ? If not   (you may have inadvertently installed it) :   uninstall it and use another search engine when you try to download Firefox again.
Note :   'Elasticsearch'  is not malware.

Certficat error..?

Hi again   !
You didn't mention this yesterday   ........
When you tried to download Firefox,   did you try to do that here :
https://www.mozilla.org/firefox/all/   ?

Seperate issue :
I notice that you're running Bitdefender Anti-virus. It would be wise to disable that   (for now),   as the program is causing problems at the moment  (and you don't need anymore of those,   do you   ?). If you're using Windows Defender :   that,   plus the safest browser on the planet   (which is of course Firefox),   is like being in Fort Knox   !

And just now I also noticed that you have a lot of plugins installed.
If you intend to keep using them   (a little longer) :   you should download the ESR Firefox version, which you can download from here :
https://www.mozilla.org/firefox/organizations/all/
Further information : The regular release of Firefox 52+ only allows one plugin, which is Flash. The Extended Support Release (ESR) of Firefox 52 + will still run Java, Silverlight, etc. Windows Users: When you get to the ESR installer list, you'll notice at least two different downloads for Windows: • Windows installer is the standard version for Windows that runs on both 32-bit and 64-bit Windows Vista through 10 (and 32-bit XP), the best choice for most users. • Windows 64-bit installer ONLY runs the Flash and Silverlight plugins.

I took some close looks at the screenshots you provided   (including the one you tried to start a new thread with),   and just to be on the safe side I would ask you to do a malware check with several malware scanning programs :
Please scan with all programs because each program detects different malware. What one program may noy detect - the other will. All these programs have free versions.

• Malwarebytes' Anti-Malware: http://www.malwarebytes.org/mbam.php • AdwCleaner: http://www.bleepingcomputer.com/download/adwcleaner/ http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml • SuperAntispyware: http://www.superantispyware.com/ • Microsoft Safety Scanner: http://www.microsoft.com/security/scanner/en-us/default.aspx • Windows Defender: http://windows.microsoft.com/en-us/windows/using-defender • Spybot Search & Destroy: http://www.safer-networking.org/en/index.html