I want him back, but I just don't know how to go about it.

我希望他回来，可我就是不知道怎么去做这件事。

《柯林斯英汉双解大词典》

But I just don't know how to distinguish myself.

但我就是不知道如何让自己与众不同。

youdao

But I just don't know. I don't know if I can do a good job with it.

但是我就是不知道，我不知道可不可以做得好。

youdao

But they don't I don't know, it's just -there isn't enough initiative in the world, not many people do it.

但是他们没有这样做,我不知道,也许只是,主动性不够,没什么人这样做

耶鲁公开课 - 金融市场课程节选

But for me, I like to look at something and just say, "I like this. I don't really know why though."

但对我来说，我喜欢看着某个东西，然后说，“我喜欢这个。但我也不知道为什么。”

关于现代美术 - SpeakingMax英语口语达人

Yes, I see them in the text just as anybody else does, but since I don't really know what they mean except by means of the translation, why should I use them?

我看着这些原版书，但是我也不懂他们真正什么意思,除了它们翻译过来的意思，所以我干嘛费劲去用俄语？

耶鲁公开课 - 文学理论导论课程节选

"I believe we've gone over the last hurdle, but I just don't know, " said Senator McCain.

BBC: US campaign finance 'set for overhaul'

One might therefore think that I should now somehow be against euthanasia, because some miracle might happen, but in reality I just don't know.

BBC: You are in: Talking Point

But I know that they don't -- but I know they don't want to just offer nothing to the millions of people in America who are in the situation that that woman was in.

WHITEHOUSE: The White House