Welcome to Android Central! First, try forcing a shutdown by pressing and holding Power and Vol Down for about 15 seconds. Then power back on, and see if the Setup Wizard asks you first for which language you want to use.
If that doesn't help, then use another device to take pictures of the screen, and use Google Translate to figure out what steps of the setup process you're at. Once you've finished the Setup Wizard, go to the system settings to change the system language.
Or go to your local Vietnamese restaurant, enjoy a good bowl of pho, make friends with the waiter, and ask him or her to translate for you.