yes. we don't use "to" sentences with pronouns, and especially not with ja/ty/my/wy. Although you would be understood.

The way you are saying this would be dirrectly translated to "You a human" You have to use the Polish word "Jesteś" which means, You are.

I also advice you dont compare languages as even though they are similiar they have many differences.

Phonetics, I guess. -kem or -gem don't really exist in Polish, they have to be softhened.

https://forum.duolingo.com/comment/16373167