First language counts as fluent language?

I’m wondering whether the languages that participants enter as “first language” also count as fluent languages.
Or asked differently: if my study screens for people who are fluent in German, will it include participants who entered German as their first language?

Thank you for the help!

Dear i_s
Welcome to the community.
I am sorry I did not respond sooner.

The questions regarding first language and fluent language are separate.
What is your first language?
Which of the following languages are you fluent in?
Participants could therefore submit English as their first language but forget (or otherwise fail) to include English as one of their fluent languages. They could also list their first language, e.g. English, as a fluent language, but fail to respond to the “What is your first language” question.