When I open a New Tab, there's always some kind of search engine I never used. First it was " Chatzum " and now it's some kind of magnifying glass with a spinning color wheel. When I go to work I use FireFox also and when I open a new Tab it give new all my common used web pages.
So I really want to remove those web browser out.
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Try to use the SearchReset extension to reset some preferences to the default values.
Note that the SearchReset extension only runs once and then uninstalls automatically, so it won't show on the "Firefox > Add-ons" page (about:addons).
If there is a problem with searching via the default about:home page then try to reset the search engine used on the about:home page.
Reset the browser.startup.homepage_override.mstone pref via the right-click context menu to the default on the about:config page and close and restart Firefox to restore the about:home page to its default.
If this didn't help then delete the delete the chromeappsstore.sqlite file in the Firefox Profile Folder and repeat the above.
Create a new profile as a test to check if your current profile is causing the problems.
See "Creating a profile":
If the new profile works then you can transfer some files from an existing profile to the new profile, but be careful not to copy corrupted files.