Many hands make light wrok. 众人帮手好干活.
The grass is always greener on the other side.
东西总是别人的好,可以另外表达为：外国的月亮总比中国的园.
Too many cooks spoil the broth.
人多误事
The early bird catches the worm.
早起的鸟儿有虫吃