hello, you have various suspicious and probably malicious addons present, which likely cause this issue. please perform all these steps:

1. reset firefox (this will keep your bookmarks and passwords)
2. afterwards go to the firefox menu ≡ > addons > extensions and in case there are still extensions listed there, disable them.
3. finally run a full scan of your system with different security tools like the free version of malwarebytes and adwcleaner to make sure that adware isn't present in other places of your system as well.

Troubleshoot Firefox issues caused by malware

The refreshing Firefox seemed to work. When I checked back there were obviously some addons which shouldn't have been there - i was not aware that they shouldn't be there - but rfefreshing removed them. I had already done the malwarebytes scan. Thank you very much.