YOU SAID:
Hello! i am very dumb and young.
INTO JAPANESE
こんにちは!私はとても愚かで若いです。
BACK INTO ENGLISH
Hello! I'm very stupid and young.
INTO JAPANESE
こんにちは!私はとても愚かで若い。
BACK INTO ENGLISH
Hello! I'm very stupid and young.
That didn't even make that much sense in English.