Managing 2 wordpress sites in different language with 1 domain

Hello.

I have a page called bananadog.jp, which is a English site. To make this website available for Japanese users, I am willing to make a clone page of this site with same content and theme, only that it’s written in Japanese. This is not working.
https://www.bananadog.jp/ (Englsih)
https://www.bananadog.jp/jp (Japanese)

I’ve installed wordpress and theme in the /jp folder, this works fine. However, the main English site gets overwritten when I make updates on the /jp folder. Is there a way to manage 2 different sites in one domain without overwriting one another?

Sorry for my poor explanation skills. Thank you very much in advance, let me know if you need further explanation.

Regards,
Shiro