I'm learning Polish, and spelling (rz dz sz cz ł and ą ę ż ś) is all fine for me-- the thing I struggle with is the grammatical cases. The fact that the ending of everything changes is what has caused me to give up twice 🥺
I will pick it up again, but I sucked at the Masculine/Feminine thing with French, and this is a lot more difficult.
CAT:
KOT
KOTA
KOTU
KOTEM
KOCIE <--- (This is where I quit: Locative case took the T away WTF?!)
The T turning into C is called somehow, I don't remember how, but it's used quite often. For example, "expensive" and "more expensive" would be "drogo" and "drożej". I think there were even some tables for all the transformations, but I might misremember things
Looks weired but a sound of C and T has to be somehow connected, at least it feels like they are to me. Based on my experience, sound of Polish Ć and Czech Ť are transitional between Polish/Czech T/C. Proper linguist might put some more light on it than just my speculation.
Polish C is also described as /t͡s/ (e.g. co /t͡sɔ/). According to wiki both are dental and voiceless although one is plosive and the other affricate. As I've read their descriptions on wiki, they made a lot of sense - /t͡s/ starts with a blockade of airway (just as /t/) but the air is released slightly differently thus making the difference in sound produced.