Learn French: C'est le réalisateur dont je parle souvent. - It is the director I often speak about.

We use dont because the verb is parler de (to speak about). The relative pronoun dont replaces the preposition de plus the person or thing you are talking about. Think of it as meaning "of whom" or "about whom".

In English, the sentence ends with "about" ("speak about"). Why is there no translation for "about" at the end of the French sentence?

In French, you can never leave a preposition dangling at the end of a sentence. The concept of "about" is already packed into the word dont. The literal structure of the French sentence is closer to "It is the director about whom I speak often."

Why does the sentence start with C'est instead of Il est, since we are talking about a specific man?

You must use c'est (instead of il est) whenever you introduce a noun that has an article in front of it, like le, la, or un. Because we say le réalisateur (the director) rather than just the profession on its own, c'est is required.

Why does souvent come after the verb, unlike the English "I often speak"?

In French, adverbs cannot separate the subject pronoun (je) and the conjugated verb (parle). Short adverbs like souvent (often) must be placed immediately after the conjugated verb. Therefore, "I often speak" becomes je parle souvent.