In order to acquire Chinese language better, most foreign students choose to HSK preparation program in China to study, hoping to study effectively. Indeed, you can learn many language points in learning program. However, if you want to speak influent Chinese, you must practice more because practice makes perfect. And the point you need to focus should be the frequently used oral expressions. Several common expressions will be explained in meanings and application to help you communicate with Chinese people smoothly.
First of all, the word 随意 is often used to tell the other party not to feel rigid or reluctant and can dine or drink according to one’s own hobbies or will. To illustrate simply, it means to be natural and at will. Usually it used on formal occasions, carrying the tone of great respect. For example, you can say 来，请入席吧，大家随意啊. If you want to mean somebody’s decision, behavior or something can’t be changed and the speaker has to let it go as it does, you should use 随他去吧, carrying the tone of having no choice but to accept it like 儿子大了，我也管不了了，随他去吧.
Of course, 随便 is also frequently used in daily conversations to show the speaker would like to be at somebody’s disposal or follow somebody‘s decisions. You can feel the meaning and tone in the following dialogue. A:你看，咱们点什么菜？B:随便，我吃什么都行. Sometimes, it can also be 随…(的)便, carrying the tone of letting things drift or not paying any attention to it like那就随他的便吧.
Teachers may also teach you the application of 算什么呀when you attend to one-on-one Chinese learning programs. It is to show that it should not be done like this and the speaker does not take what happened or the person mentioned very seriously. When used to make comment on a person, it carries the tone of modesty if this person is the speaker himself like 人家是专家，我算什么呀. Otherwise, it shows the contempt for the person commented. If it is 算怎么回事啊, it can only be used to refer to things instead of persons.