[Django]-How to get value from choices in Django?

Just return a str function from your AvailableLanguage model:

class AvailableLanguage(models.Model):
    LANGUAGES = (
        ('en', 'English'),
        ('ru', 'Russian'),
        )
    lang = models.CharField(max_length=50, unique=True, choices=LANGUAGES)
    lang_code = models.CharField(max_length=5, unique=True)
    slug = models.SlugField()

    def __str__(self):
        return self.get_lang_display()