Your admin strings are untranslated in the site’s backend because WPML does not display translations of admin strings in your site’s backend. This means you will always see these strings in the default language, even if you have translated them and changed your user language. The translations will display on your site’s front-end or in AJAX requests.
Let’s say we want to translate our site’s tagline from our default language, English, into a secondary language, Spanish. The tagline is an example of a string that appears both in our site’s admin (by going to Appearance → Customize and clicking Site Identity
We can translate this string by going to WPML → String Translation and searching for “tagline” in the text search. If you aren’t able to find a string you want to translate on the String Translation page, you can add it to the String Translation page.
Translate the string by clicking the icon under the appropriate flag.
Now, the new Spanish tagline will appear on the front-end when a client views the page in Spanish.
If your profile language is different from your site’s default language, this can be confusing. For example, let’s change our profile language to Spanish. You can do this by going to Users → Profile and choosing Español from the Language dropdown menu.
If we navigate to Appearance → Customize and click Site Identity, we still see the tagline in English, the site’s default language, even though a Spanish translation exists.
However, on the site’s front-end, we see the Spanish translation when we switch to Spanish, as expected.
This is the expected behavior of such strings. The reason the string appears in the default language in the backend is to prevent conflicts between this text entry field and any translations that may exist.