Translation:He is fine.
No. Hajambo refers to third person singular (he/she). Hujambo is second person singular (you). Also, this sentence doesn't end with a question mark, so it is not a question.
Hujambo more literally it means "you have no problems". As in English, a sentence can become a question through intonation, so it can also be "you have no problems?" As a question is equivalent to "how are you?" in English, and as a statement it serves as the answer.
I think most often hujambo and hamjambo will be heard as questions, sijambo and hatujambo as responses ("hujambo?" "sijambo" / "hamjambo?" "hatujambo"), whereas hajambo and hawajambo will go both ways ("baba hajambo?" "hajambo" / "watoto jambo?" "hawajambo"). But don't quote me on that.