I downloaded Firefox to quit using chrome but Google is the default browser! I thought that Firefox was a browser in its own right.

Firefox is a web browser while the Google you are seeing in Firefox is likely as a search engine. To use or install another search engine in Firefox for Android see https://support.mozilla.org/en-US/kb/manage-my-default-search-engines-firefox-android Just to be clear, Firefox is not a search engine as a search engine is for example qwant.com, google.com, duckduckgo.com, bing.com etc.