Learn Polish: Bez nadzoru szefowej ci młodzi ludzie nic nie zrobiliby. - Without the female boss's supervision, these young people would not have done anything.

The preposition bez (without) followed by the Genitive case acts as a shortcut for an hypothetical "if" statement. It essentially means "If it weren't for the female boss's supervision" (Gdyby nie nadzór szefowej...). Using bez + Genitive alongside a conditional verb like zrobiliby is a very natural Polish way to express a hypothetical situation without needing a full dependent clause.

Why does the noun szefowej have the ending -ej, which usually belongs to adjectives?

The word szefowa (female boss) was originally formed by adding an adjectival suffix to the masculine noun szef. Because of its origin, it declines exactly like a feminine adjective. Since the phrase requires the Genitive case to show possession ("whose supervision?"), the feminine adjective-like ending becomes -ej.

Why is the pronoun ci used instead of te before młodzi ludzie?

The noun ludzie (people) is masculine personal (virile). In the plural, Polish strictly divides nouns into masculine personal and non-masculine personal. Because ludzie implies there might be at least one male in the group, the demonstrative pronoun must be the masculine personal ci (these), and the adjective must take the masculine personal form młodzi.

Could we detach the conditional particle -by from the verb zrobiliby?