Learn Turkish: Birinci oturumda konuşacak kişi çok önemli. - The person who will speak in the first session is very important.

In this lesson, we see the future tense suffix -acak / -ecek being used as an adjective. Just like konuşan kişi means "the person who speaks", konuşacak kişi means "the person who will speak". It attaches directly to the verb stem konuş- to describe the noun kişi that follows it.

Why is all the information about the session placed at the very beginning of the sentence?

In Turkish, the entire descriptive phrase must come before the noun it modifies. The phrase Birinci oturumda konuşacak (who will speak in the first session) acts as one big adjective modifying the noun kişi (person).

Does the word oturumda come from the verb oturmak (to sit)?

Yes, it does! Oturum literally means a "sitting" and is the standard word for a "session" at a conference, a meeting, or even logging into a computer. With the locative suffix -da, it means "in the session".

Why doesn't the sentence end with a "to be" suffix like -dir?

In everyday Turkish, the third-person "to be" suffix (-dir or -tır) is often left out. The sentence ends with önemli (important), and the "is" is simply understood from the context. You could say önemlidir, but leaving it off sounds much more natural in everyday speech.