You can't add more language pairs. After creating an account on Fairlingo, you can translate to your native language from one source language. It's not possible to change your chosen native language, so make sure you select the right one. You can change your source language.
Changing the source language
1: Log in and go to profile & settings (figure 1)
2: Click on profile and delete your translation skills (figure 2)
3: Add the new source language (figure 3)
4: You will receive notifications for assignments in the language pair you added to your profile.