It's OK—hang loose and stay cool.

没事儿，你要镇定，要冷静。

《牛津词典》

OK, so let me finish with a cool example.

我们用一个很棒的例子来结束这节课。

youdao

OK, cool, glad we cleared it up!

好的，酷，很高兴我们厘清了！

youdao

OK, any questions? Cool.

有问题吗？好。

麻省理工公开课 - 热力学与动力学课程节选

OK cool All right, a couple. OK, cool.

有几个。

麻省理工公开课 - 化学原理课程节选

If you want to start eating pizza for breakfast and stay up too late watching HBO and let yourself go a bit it's totally OK. Everyone will be cool.

WSJ: Rivera's So-Called Retirement