Hello Ania,
That is great, motivation is very important in language learning process and I'm sure it will help you to progress 😀
A very nice idea to incorporate Polish into English! Would you like me to point out a very minute mistakes in your sentences?
yes TAK always prosze correct me - I don't know why the polish alphabet is not coming up in this response.
Great!
Polish z changes case to instrumental of the adjectives and nouns that come after. You have used nominative case.
Instrumental case (narzędnik) Z kim? Z czym? z moją bratową
Nominative case (mianownik): Kto? Co? z moja bratowa
One more correct example. Moja bratowa (nominative) mieszka w Polsce. W weekendy spotykam się z moją bratową (instrumental).
mózg is a masculine noun, so mój mózg not moja mózg
muzyka is a feminin noun so piękna muzyka not piękny muzyka