It would be presumptuous of me to comment on the matter.

我如果对这件事发表评论会很冒昧

It would be presumptuous of me to assume that I know more than the experts on this subject.

在这个问题上，如果我认为我比专家懂得多，那就太自以为是了。

I thought it was presumptuous of her to invite herself to my party without asking me first.

我觉得她没有事先问过我就不请自来参加我的派对，太放肆了。

It would be presumptuous to judge what the outcome will be.

断定结果将会如何未免冒失。

It is too presumptuous of him to do so.

他这样做太放肆了。

One should never be presumptuous and opinionated.

切不可自以为是。

Don't make presumptuous comments out of ignorance. Don't make improper comments before you know the whole story.

不要不明原委， 就妄加评论。

You're very presumptuous, no?

你太自以为是了，不是吗？