https://chromlea.com/polish/numbers.php
so, "dziewięćdziesiąt dziewięć" is something like "the ninth ten plus nine," (i think), which is not that complex, but the fucked up part is that numbers five and above have a completely different case ending.
also, in english our 20, 30, 40, etc numbers all end in -ty. twenty, thirty, and so on. polish changes it up:
20 = Dwadzieścia
but
30 = Trzydzieści
similarly,
40 = Czterdzieści
but
50 = Pięćdziesiąt
and so on until 100 (sto).
like the language is hard enough as it is and has way too many letters, but then all these pattern shifts makes everything just impossible to memorize.