Correcting a Spelling Mistake

I found a spelling mistake in the German version of the plugin and I am not able to correct it.

It is in the booking form. At the end you have to tick a box that you agree that your information can be processed by the site. The first word is the English “I” instead of the German “Ich”. I already went into includes/langs and the PO-file but couldn’t find it there.

Where can I change it?

Thank you,
Sam

The page I need help with: [log in to see the link]