Firefox is available for Windows, MacOS, Linux and Android. It is "open-source" software which means that anybody can see the computer code and suggest improvements - these are considered by Mozilla (which produces it).

Chrome (available for Windows, MacOS, Linux and Android) is also open-source. Suggested improvements to it are considered by Google, which releases it.

I use both Firefox and Chrome.

As far as anti-malware software is concerned, AVG is good. Malwarebytes is also worth checking out. It is available for Windows and Android and (in my experience) efficiently zaps malware on my laptop on the rare occasions that it gets infected.