https://support.mozilla.org/en-US/kb/manage-my-default-search-engines-firefox-android

https://support.mozilla.org/en-US/kb/add-or-remove-search-engine-firefox https://support.mozilla.org/en-US/kb/change-your-default-search-settings-firefox

Since you posted about desktop Firefox in the Firefox for Android section. You can add whatever search engine you want and change what is the default search engine.

on my pc i open firefox and duck duck go is my default search engine. On my andriod phone i open firefox and the default search engine is google. I hate google, i hate even more that firefox will not let me change from google to anything else

See https://support.mozilla.org/en-US/kb/manage-my-default-search-engines-firefox-android#w_add-a-search-engine

As I linked earlier it tells you how to add a search engine in Firefox for Android.