hello maderaroja, go to firefox > addons > extensions and remove the zoomex addon - it is probably malicious.

Troubleshoot Firefox issues caused by malware

afterwards install the search reset addon - it will revert the most common customizations those adware programs do in firefox back to the default: https://addons.mozilla.org/firefox/addon/searchreset/

also run a full scan of your system with security tools like the free version of malwarebytes & adwcleaner.

I have done as suggested with the first instruction and removed zoomex. I do not understand the second instruction about installing the "Search reset addon".

i've recommended the search reset addon, because some sort of adware has overwritten the search engine that is used when you enter a term into the address bar.

all you have to do is click "add to firefox" on https://addons.mozilla.org/firefox/addon/searchreset/ & confirm the installation dialog. then the extension will install, reset the preference i've talked about above and uninstall itself from firefox again and you should be all set.

Thank you for your help and the clear instructions. You should sign your work. You would get a kudo from me.