Translation of Strings from other plugins

Hello, could you please help me translate strings from other plugins?
For example here: https://dago.brofi.eu/en/inquiry/ For example here https://dago.brofi.eu/en/inquiry/ “Soubor nevybrán” (cotact form plugin)

I check section string in administration, but i did not find any of them

Thanks for any advice

Jan
PS:By the way thanks for your great plugin

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