YOU SAID:

he cheated on me so i broke his ipone

INTO JAPANESE

彼が私をだましたので、私は彼のiPhoneを壊しました

BACK INTO ENGLISH

I broke his iPhone because he cheated on me

INTO JAPANESE

彼が浮気したのでiPhoneを壊してしまいました

BACK INTO ENGLISH

I broke my iPhone because he cheated on me

INTO JAPANESE

彼が浮気したのでiPhoneを壊してしまいました

BACK INTO ENGLISH

I broke my iPhone because he cheated on me