I always hear Chinese people making sentences using 而已 - but I've never quite 100% how to use this in sentences myself. What is the correct way to apply it, and what is the English equivalent?
“而已” is always used at the end of a sentence and with words like “仅仅”,"只","不过". A similar word in Chinese is "罢了"(actually, this word comes from 满语). You use the structure "......(part A),不过......(part B)而已" to emphasize the expression that A is just limited within B. You could only use "不过", also, and "而已“ weakens your mood and sometimes expresses that you don't have help to (or don't take care of) B.
The equivalent for the structure "不过......而已" would be "only","just".
The easy way to understand this is to use an oral English sentence rather than something formal. This is commonly used to mean "...and that's all".
For example in English you can say "It's just an exam and that's all".
In Chinese this could be said: "这不过是一个考试而已" Zhè bùguò shì yīgè kǎoshì éryǐ