It looks like you think Firefox for Android is a search engine when it is a web browser. A search engine for example is duckduckgo.com, google.com, bing.com etc. The company Mozilla does not have a search engine service of their own. You can use a wide variety of search engines in the Firefox web browser on Android https://support.mozilla.org/en-US/kb/manage-my-default-search-engines-firefox-android