You can customize all custom language strings for Edumy Moodle LMS theme with these steps:

1. Go to Site administration -> Language -> Language customization 
2. Choose the language you wish to customize
3. Once the language pack is loaded, click “Continue”
4. Under “Filter strings”, choose “theme_edumy.php”, and click “Show strings”
5. Now you will be able to customize all custom Edumy language strings for your language

On this page you can also search for particular strings, like "login" for example.

After you have customized the strings for your language, you can save your changes.

Then it's best to purge all Moodle caches, and everything should be looking great.

For multilingual sites (websites running multiple languages), Edumy also supports filter_multilang2: https://moodle.org/plugins/filter_multilang2

As such, we recommend a combination of language string translation (using the steps above), and multilingual translation using filter_multilang2.