I simply don't know if I'll ever get it finished.

我简直不知道我是否能完成它。

youdao

You're all so nice to me. I simply don't know how to repay your kindness.

你们待我太好了，我简直没法报答你们。

youdao

"He should quite simply resign."—"I don't know about that."

“他只要辞职就行了。”—“我说不准。”

《柯林斯英汉双解大词典》

I simply don't know because my history isn't very good. So, sorry.

我不知道，是因为我的历史学得不好。所以，很抱歉。

英国电影的魅力 - SpeakingMax英语口语达人

I want to quote from the beginning of Roland Barthes' essay, which I know I only suggested, but I'm simply going to quote the passage so you don't have to have read it, The Death of the Author.

我想引用罗兰，巴特文章开头的几句话，我只是推荐这篇文章，从中引用几句,所以你们不用事先读，这篇文章就是《作者之死》

耶鲁公开课 - 文学理论导论课程节选

Now when I look at those beads, they simply remind me that I don't ever know as much as I think I do, but I'm always capable of more than I think I am.

NPR: I Am Capable Of More Than I Think I Am

However, even with all my technology expertise I still get frustrated from time to time - there are things I simply can't figure out or don't know how to do.

BBC: Three missing ingredients of small business technology

Mr. WEISBERG: Yes and I think the volatility, basically, is just indicative of the fact that people just simply don't know what to do and so everybody is sort of sitting on the head of a pin, easily pushed one way or the other depending on the headline or rumor.

NPR: Floor Trader Describes Wall Street Gyrations