How to manage search engines access for Firefox on Android device

If you use Firefox on your Android device, you normally get hits from Google, Amazon, Twitter and Wikipedia when you search for a keyword. If you want to limit the search only to Google or want to extend it to other search engines like Yahoo, you do not have the option to manage the search engines
from the search box like on the PC.
The configuration of search engines is available in the add-ons menu. For this, open the settings of the app and the tap on "Extras" and then on “Addons”. Besides other possible extensions this list shows the set search engines where the aforementioned four search engines are integrated. In order to switch off any one of it, tap on it and then on “Deactivate” in the following dialog. With the same method, you can later reselect the search engines later by tapping on “Activate”. To insert additional search engines, tap on the icon to the right next to "Your Add-ons". Only in the following dialog, enter the search keyword as “Yahoo” or “Bing” in the field on the page and then tap on the green arrow. Search for the suitable add-on such as “Yahoo Search for Firefox Android” in the list. Then open the detailed display and tap on “Add to Firefox”. Confirm the request for the new search machine by selecting “Add”.