In General , we have an Account Setting in DTM Interface where a user choose the desired language from the drop-down list. The user interface displays in the selected language. In the upper right corner of the dynamic tag management interface, click > Account Settings and screen like below screen will be displayed. Please check whether the correct language option is selected or not.
If the correct language option has already been selected , Can you please let us know whether the label language problem exists only on the Rules section pages or on all pages of DTM Interface?.
The interface should be pulling from the language setting. For this issue, I recommend opening a ticket with Customer Care for further investigation. In the ticket include the property name and an example rule where this occurs.