How to change the site language?

Question

CMS

Hello, such a question, I'm new to the topic of creating websites, but I'm trying.
I downloaded the finished site, put it on the local network and sorted it out a little, but then I noticed that this site does not have a button to change the language, i.e. only Russian and that's it. Actually the question is how to change the language on the site? If you only change it once, it’s understandable - to translate everything that is Russian, but you need a multilingual site))
I had the idea to create another site at the root of the main site and name it "en" and it turns out such an address is localhost / en / and immediately ran into the problem is that all values ​​where the site root is specified will go to the site root, and not to the address localhost / en /, and these are all values ​​\u200b\u200band it turns out there is no point in this en. How to be? I tried to add "/en/" by mass replacement where it was possible, but no.
CMS: SocialEngine, copy of social media, twitter, facebook

Answer 1

https://support.socialengine.com/php/customer/port...
https://support.socialengine.com/php/customer/en/p...

Answer 2

Downloaded the website

I understand you got a bunch of static pages, but modern sites are dynamic. They don't have static html files, they generate them on the fly.
So start by understanding dynamic sites. And everything will become clear. For example, read about php.