Basic Translation?

Hi,

I started to use Strong Testimonials plugin on a website. The website is only in German, no other language.

I am wondering how I can translate the two fields:
“Required”
“Add Testimonial”-Button

I′d like to do it without installing a translation plugin – is this possible?

Here is the screenshot: https://pasteboard.co/6ysHDMSgFbKT.jpg

Best regards and thank you in advance
Markus

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