YOU SAID:

I am 20 years old! That makes me one of the oldest persons alive

INTO JAPANESE

私は20歳です！それは私が生きている最も古い人の一人になります

BACK INTO ENGLISH

I am 20 years old! It will be one of the oldest people I live in

INTO JAPANESE

私は20歳です！それは私が住んでいる最も古い人の一人になるでしょう

BACK INTO ENGLISH

I am 20 years old! It will be one of the oldest people I live in