wrong label language

hi

i run a german website, but english and german is active on my site. i created a signup-form block with email address, first name and last name. email-address is korrekt on the site but for "First Name" and "Last Name" are still the english versions there instead of the german one. when i go to the translate surface page and search for "First Name" it finds it but it mixed the languages - the german words stand on the english side and opposite. how can i fix this?

thanks+greets