Comparative adjectives

Mam takie dwa przykłady:

1. I work best when I'm not feeling tired.
2. I'm learning French, Italian and Spanish. Of the three languages, I speak Italian most fluently.

Dlaczego tutaj ominięte jest 'the'. Czy ze względu na brak rzeczownika?

Yes, 'the' can be omitted, especially in informal situations.

1. The relevant domain (current discourse space) within which the uniqueness is to be established is not obvious. Here best is equivalent to (very) well or better than (when I am tired.)

2. "the most fluently" would mean your French and Italian are also fluent, which is supposedly not what you mean to say.