I can run fast.

我能跑得快。

《牛津词典》

I can run fast, but you can't.

我能跑的快，但是你不能。

youdao

I can speak English. and I can run fast.

我可以说英语和我可以跑的很快。

youdao

This is very important,which is why I am doing it: "If we want to know how fast a human being can run, then it is no use to average out the speed of a "good sample" of the population; it is far better to collect Olympic gold medal winners and see how well they can do.

这话非常重要，是我作这个研究的原因：,“如果想知道人类最快能跑多快，那从好的样本中测出平均数是“,没用的;,而应该收集田径类奥运冠军的信息,看他们能跑多快。

哈佛公开课 - 幸福课课程节选

If she is on her leash she runs right next to me but I know she can run really fast.

CNN: A boy and his seizure dog