To add more languages to the code,

1. You expand the res folder in your android studio, then the values folder.

2. Right click on the strings.xml file -> New -> Values resource file, then this box pops up 3. Then select Locale and click the small box with the moving forward arrow then you choose the language you want to create and region the language originates from. Make sure the flags of the language and region is the same to prevent errors. 

Also the file name has to be strings. Then click ok.

An empty string file would then be opened. 

The only difference that can be in all string files is the language of the texts in black, all other thing would remain the same as it is in the english string file.

Here, the app_name and facebook_app_id can be changed too.