Type about:addons<enter> in the address bar to open your Add-ons Manager. Hot key; (<Control> [Mac=<Command>] <Shift> A)

In the Add-ons Manager, on the left, select Extensions. Remove “ Bing “ Anything.

Also remove SafeSearch, SearchAssist Incognito, FileConverter Addon, SearchLock, DiscreteSearch, WebSearch, Findwide Search Engine, securedsearch

Now do the same in the computer’s Programs Folder.

Windows: Start > Control Panel > Uninstall Programs. Mac: Open the Applications folder. Linux: Check your user manual.

Excuse me I have posted another Post. But this is not a solution for me. As I have only DUCKDUCKGO as addon (Extensions) activated, nothing else. None of the Programms state above are in my programm folder.

Start Firefox in Safe Mode {web link}

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Must I start FF always in Safe Mode oder only once? After starting in Safemode and Restarting FF again, DDG (Duckduckgo) was there and is OK. But I will watch for some time.

I am sorry. The problem ist still there. Bing is the starting page, though I don´t want it. In Settings I have not Bng as the staring Page.

Now I have found the mistake. My starting Page was wrong. After I have changed it is all OK. Thank you very much.

Glad to help. Safe Surfing.

https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes), any userChrome.css/userContent.css files, and some other advanced features to help you assess whether these are causing the problem. If the problem goes away, that tells us one thing. If it does not, that tells us something else.