What does "nežli" means? I guess that it's 3p plural (neg) of a verb but I do not know it's infinitive and can't find it in the dictionary. It's from a song of Nohavica (the part of the song is: "tma horší byla nežli v pytli")
Nežli = než, means 1. than, 2. before Similar to it is the combination "zda" and "zdali". The suffix -li is so-called intensifier. Examples: Lepší než(li) ty = better than you Budu doma, než přijdeš = I will be home before you come "Tma horší byla nežli v pytli" = it was darker than in a bag
BTW - "nežli" can be found in some colloquial (rather obsolete) Czech as 3rd plural of the verb "žnout, žít" "nežali" = they did not reap. So your way of analyzing an unknown word was not wrong at all (-li as the past tense suffix for plural).