Learn Turkish: Açılış ve kapanış yapacak kişileri seçmek gerek. - It is necessary to choose the people who will do the opening and closing.

While it looks exactly like the regular future tense "will do", here it is a future subject participle. It acts as an adjective modifying kişileri (the people). Just like yapan kişi means "the person who does", yapacak kişi means "the person who will do".

Why does kişileri have the accusative -i suffix?

It is the direct object of the verb seçmek (to choose). Because the phrase açılış ve kapanış yapacak (who will do the opening and closing) defines exactly which people are being chosen, the noun is specific. Specific direct objects always take the accusative case.

What does the -ış suffix do in açılış and kapanış?

The -ış / -iş suffix creates a noun out of a verb, representing the action itself or the way it is done. Here, açılmak (to be opened) becomes açılış (the opening), and kapanmak (to be closed) becomes kapanış (the closing).

How does seçmek gerek work? Could we use a different structure?