Hey Sebastian,
all text strings in Kanso have been wrapped in proper WordPress functions, thus they can be translated with any internationalization plugin. In case you are making your website in German only (i.e. no multilingual support is required), I would suggest using the Quick Localization plugin.
Once you install the plugin, you can see that if allows adding sets of fields, where “Old” is the existing string (please note that the strings in WordPress are case-sensitive!), “New” is the new desired string, and “Domain” should say “satori” (without quotations marks) for each new set of fields.
If you are familiar with coding, another (cruder, yet simpler) option would be to just edit the file that generates the strings – it should be located in /wp-content/plugins/contact-form/grunion-contact-form.php). All translatable strings are wrapped in the translation functions “__()” and “_e()” as detailed here.
In case of difficulties with any of the methods do not hesitate to contact me!
Best,
Andrii / Satori Studio