One domain 2 installation or translation

Hi all,

I know there is similar thread here but my question is not answered.

I have domain https://www.domain.com – wp instalation
I would like to have https://www.domain.com/en -wp instalation english
https://www.domain.com/pl – wp instalation polish

But by default i want to have english version as a first to open/

I thought I will do it by making second instalation. Any ideas please?