I have had the Priv for about two months now. You must have been using the carrier version as the wireless charging is not included and maybe why you felt the back was wobbling (sort of bending in towards the front of the phone)
Changing the input language could not be easier. Settings>Language and Input>BlackBerry Keyboard Settings>Multi-language keyboard [Make sure Use System Language
is turned off, and start adding languages.
To quickly change language hit the keyboard key and it should look like this..