how can I change the language of the site?

I prefer having this in English but this shows Portuguese instead. Can someone help me with this?

Click in the name than in the language and then keep whatever you want

Thanks, that was useful. I was looking everywhere at the settings but it was just on the name.

I misread that as "how can I change the Lagrangian of the site?" and was confused

I need to take a break from calculations!!!