Okay, I understand. And I'm happy to tell you that 'personel' also refers to a group of workers :) Even if it's singular, that's still for a group. (the word 'group' itself is singular in Polish)
I guess you could say "członek personelu" to denote "member of the staff", but "pracownik" (worker, employee) would sound a lot more natural.
I understand - thank you. By the way, in modern spoken English, groups seem to float between being singular and plural, so you can say "England is out of the competition" but more commonly, "England are out of the competition", even though that would have been considered wrong a few decades ago.
I always hear this as "England is out of the competition = The team that is England is out of the competition" and "England are out of the competition = the people of England as a nation collectively are out of the competition" but you're right I hear them both equally and i don't think I've ever heard "England has/have won the competition"!
There is an interesting discussion here: www.onestopenglish.com/grammar/grammar-reference/american-english-vs-british-english/differences-in-american-and-british-english-grammar-article/152820.article. Jellei does have a point.
Staff is a singular noun and when we use it with a singular verb, that's grammatical agreement, but it's also "correct" to use notional agreement with a plural verb. This is the case with many collective nouns. British English uses notional agreement more than American English.
The following dictionary entry shows examples with grammatical and notional agreement.
"A number of people doesn’t understand notional agreement" ;)