If the program somehow switched to a language you do not understand, do not worry!
The buttons are located in the same place for all localizations, so follow these screenshots to find your way to the language settings:

1. Open Menu > Settings in the main window. Menu is in the top left corner of the program, Settings is a 7th item on the list in the drop-down menu.

2. This will open the Settings window. Here you want to open the General > Language section. General is the very top section while Language should be the second one in the list below. 

3. Then just select your preferred language and press Ok.