This is the 3378th most frequent Polish word.
wszystkimi
"All" or "everyone" (instrumental form).
The word 'wszystkimi' is derived from the noun 'wszystko', appearing here in instrumental case, used to indicate the means or method of sharing.
Dzielę się wszystkim, co mam.
I share everything I have.
In this sentence, 'wszystkimi' is the instrumental plural form of the pronoun 'wszystkie', referring to the group of friends in the sentence.
Byliśmy tam z wszystkimi naszymi przyjaciółmi.
We were there with all our friends.
Here, 'wszystkimi' is used in the instrumental case indicating 'with all' the specified individuals in the team.