If you are referring to 'completely' resetting up the device, that would mean a reset of the device. So anything you have personally added to it, files, music, apps, settings changes, contacts, etc., would be lost.
However if you haven't added much, then it would be worth it.
NOTE: Doing this will clear 'all' the data on your phone, so it is suggested you not choose this option unless you have to, or aren't worried about losing anything on the phone.
Be sure you back up any data you want to keep, to a computer or cloud account, before doing the reset.
To "Hard Reset" the phone...
1. Make sure that the phone is actually powered off.
2. Remove your SD card, if there is one in the device.
3. Press the "Power" and the "Volume Up" buttons, together, until you see the start-up logo on the screen.
4. Once you can see the logo, release the buttons and allow the device to enter the "System Recovery Mode".
5. Next use "Volume Down" button to get to the "wipe data/factory reset" option When in recovery mode the "Volume Up" and "Volume Down" buttons are how to can navigate and highlight what option you need.
6. Once you have selected the "wipe data/factory reset", press the "Power" button to select that option.
7. On the following screen, repeatedly press the "Volume Down" button until the "Yes - delete all user data" option is what is selected.
8. Then press the "Power" button to hard reset the phone.
9. If you took your SD card out in step 2, when the device is up and running again, reinstert the SD card.
OK you are going to have to do your best to locate the right words in Spanish to correlate with the words I am giving you in English, as I don't speak/write Spanish.
How to change the language on a smartphone....
1. First swipe "down", from the top of the screen, to pull down the "Notification Shade".
2. Next tap "Settings" in the top right corner of your screen.
3. On the "Settings" screen, scroll down to and tap up to Language and input.
5. Now tap "Language" and then tap the language you wish to use.
That's it. The default language on your phone should now be the one you want. All of the text on your device should appear in the language you selected. If by some chance it hasn't change yet, try restarting your phone.
Thanks, the default language is now in English. But I still had to fumble through the whole menu because the "swipe down" did not function until I got to the end of the Spanish set-up. I wonder now what items I agreed to or omitted during that set-up in Spanish? Is there a way to start the set-up menu over again, but in English?