You can do two things. You can change the widget's display language and then choose to only show reviews that match that language.
In Trustpilot Business, go to Showcase > Website widgets. Choose your widget.
Under Customize, use the Widget language drop-down menu to choose your language.
If you’ve chosen a widget that displays reviews, you can filter the reviews to only show those written in your preferred language. Once you've followed the steps above, continue:
Under Widget language, ensure the toggle Only select reviews written in this language is on.
This is the default setting. You can also switch the toggle off to display reviews written in all languages. Once you’ve made your changes, click Get code and replace your old widget code with this updated one.