Changing the display language

Hello,

First of all, thank you for developing and maintaining this awesome plugin!

The pluging installed with a German user interface on my website. Since the quality of the translation is very poor, I would like to correct some of the German strings or, alternatively, switch to the English version and re-translate parts of it with WPML. Can somebody give me a hint on how to edit the translated strings or change the active display language? Many thanks in advance!

Armin