hello anwarhussain333, this sounds like a problem possibly caused by malware on your pc. please go to firefox > addons > extensions & remove any suspicious entries (toolbars, things that you have not installed intentionally, etc). also go to the windows control panel / programs and remove all toolbars or potentially unwanted software from there and do a full scan of your system with the security software that you have in place and/or a different tool like the free version of malwarebytes.

Remove a toolbar that has taken over your Firefox search or home page Troubleshoot Firefox issues caused by malware

Also,

The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Note: This will cause you to lose any Extensions, Open websites, and some Preferences.

To Reset Firefox do the following:

1. Go to Firefox > Help > Troubleshooting Information.
2. Click the "Reset Firefox" button.
3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
4. Firefox will open with all factory defaults applied.

Further information can be found in the Refresh Firefox - reset add-ons and settings article.

Did this fix your problems? Please report back to us!

You may also have to Disable suspicious Plugins in Tools (Alt + T) > Add-ons and check.

Using plugins

If the problem persists, it could be an external Windows program (legitimate or otherwise) opening webpages at regular intervals. You can try to identify the program (it could be Television Fanatic or another name) and make adjustments in it, or uninstall it via Windows Control Panel > Programs and Features or Windows Start menu.