How to manage Search Engine List in Mozilla Firefox.

There is the button next to the Search Tab in Firefox that you can manage the Search Engines List. You can simply choose which search engine you want to be your default search engine. Moreover. You can also remove or get more search engines that are not in the list by clicking "Manage Search Engines List" then click "Get more search engines..". The Add-ons page will appear and you can choose and add as much as you want.

For google search, it will go to regional google of the location where you are. If you want to change to English version, just simply go to google page and click "Google.com in English". Then, the next time you go to search, the English page will be shown.