decydujcymi
Decydujcymi appears to be a nonstandard or misspelled form of the Polish word decydującymi, which is the instrumental plural form of the adjective or present participle decydujący meaning decisive or deciding. In standard Polish, decydującymi is used to describe nouns in the instrumental case, for example in a phrase like decydującymi czynnikami, meaning the decisive factors.
In Polish, decydujący is the masculine singular form; feminine and neuter forms are decydująca and decydujące
Etymology and meaning: decydujący comes from the root decydu- with the usual Polish suffixes that form adjectives
Usage notes: Polish participles agree with the nouns they modify in gender, number, and case. Misrendered spellings