keep up appearances

maintain an impression of wealth or well-being, especially to hide the true situation

（尤指为了掩饰真实情况而）维持门面，装门面，装体面

make (或 put in) an appearance

attend an event briefly, especially as a matter of courtesy

（尤指出于礼节而）短时间到场，露面，亮相

to (或 by) all appearances

as far as can be seen

就表面看来，就所能看到的情况而言

to all appearances, it had been a normal day.

表面上看，那是平常的一天。