can’t slack: hold fast to / stick to
e.g.
It is true that the environmental issue is becoming more and more serious than ever before, thus, we must work together and can never slack.
brush up: improve
e.g.
Factually, we are well-advised to brush up our communicative skills so as to enlarge and strengthen our social network.
raise the white flag:quit / give up
e.g.
Those pessimists are very likely to raise the white flag once they come across any trouble or setbacks in their daily life or work.
not by a long chalk: by no means
e.g.
That amount of time won’t be enough, not by a long chalk.
更多:看英剧, 学地道表达(III)http://www.huamengedu.cn/artview-130.html
简单留学，就来华盟