Learn Turkish: Saçların zaten düz, tarak kullanmana gerek yok. - Your hair is already straight, you don't need to use a comb.

This is the core structure for this lesson! It breaks down as kullan-ma-n-a. You take the verb root kullan- (use), add the verbal noun ending -ma ("using"), attach the possessive -n ("your"), and finally add the dative case -a ("to"). Because gerek yok literally means "there is no need", the whole phrase translates closely to "there is no need to your using".

Why is saçların plural ("your hairs") when the English translation says "your hair"?

In English, "hair" is an uncountable noun, so it's always singular. In Turkish, when referring to the hair on someone's head, it's very common to use the plural saçlar (and with the possessive, saçların). You can also use the singular saçın in Turkish, and it would mean the exact same thing here.

Why is tarak (comb) in its bare form? Shouldn't it be tarağı since it's the object of the verb "use"?

Turkish only uses the accusative case (like tarağı) for specific direct objects. Here, the speaker is saying you don't need to use a comb (any comb in general). Because it's a general, indefinite object, it stays in its bare dictionary form. If they meant "you don't need to use the comb" (a specific comb we both know about), it would be tarağı kullanmana.

I usually translate zaten as "anyway". Does it mean "already" or "anyway" in this sentence?