Edwiser RemUI theme is translation ready. Let's say you want to use Edwiser RemUI in Portuguese (Brazil).

To translate the RemUI specific strings to Portuguese, you need to follow these steps.
1) Navigate to Moodle installation -> theme -> Edwiser RemUI theme -> Lang folder
2) Create a new folder with the language code i.e. pt_br
3) Now copy and paste theme_remui.php from en folder to the new folder (pt_br)
4) Now add Portuguese translation besides the strings.
5) Once this is done, do Purge Cache on your Moodle site and check if the strings are translated.

Note: You need to install the Portuguese (Brazil) language pack first in the Moodle Site.

Also, you need to use the language code properly as per which language you want to use on your site.