YOU SAID:

my brother is very tall and has a nice girlfriend, but I don't know when I'll find a girlfriend

INTO JAPANESE

私の兄はとても背が高くて素敵な彼女がいますが、いつ彼女が見つかるかわかりません

BACK INTO ENGLISH

My brother is very tall and has a nice girlfriend but I don't know when he will find her

INTO JAPANESE

私の兄はとても背が高くて素敵なガールフレンドがいますが、彼がいつ彼女を見つけるかわかりません

BACK INTO ENGLISH

My brother is very tall and has a nice girlfriend but I don't know when he will find her