I checked a great number of blogs about how to build a dual-language website. Most of them need to write seperate content by myself for two languages which is not what I expected. So I finally found my own method to achieve it.
With the help of google “Website Translate” function, I solved this issue to some extent. the whole principle is simple:
https://www-jingnan--jia-com.translate.goog/?_x_tr_sl=en&_x_tr_tl=zh-CN&_x_tr_hl=en&_x_tr_pto=wapp is the translated version of https://www.jingnan-jia.com/.
So I created a link to the translated address. After going to the translated website all the following pages would also be translated.