认识和了解用英语怎么说？

you can say, "I just know him, but I don't understand him well"

I recognize him , but i can't understand him.

I know this guy,but he's not my acquaintance.

I recognize he,but I dong't know much about he(或者understand he)

我认识他，但是我不了解他。
i know him, but i don't know about him.

undeistand