Learn Turkish: Kayak yapmak zor değil.

In Turkish, infinitive verbs ending in -mak or -mek can act as nouns. This is just like adding "-ing" to a verb in English to make it a subject (a gerund). Here, yapmak acts as a noun, making kayak yapmak mean "skiing" or "to ski".

Why do we need yapmak? Can't we just use a single verb for "to ski"?

Turkish doesn't have a single dedicated verb for "to ski". Instead, it pairs the noun kayak (ski) with the helper verb yapmak (to do / to make). You will see yapmak used this way with many sports and activities, like spor yapmak (to exercise) or piknik yapmak (to have a picnic).

Where is the word for "is" in this sentence?

In Turkish, the third-person "is" suffix (like -dir or -tir) is often dropped in everyday speech and writing. While you could technically say zor değildir, just saying zor değil is completely natural and grammatically correct.

Could I use yok instead of değil to say "not hard"?

No, because yok means "there is not" or "does not exist". When you want to say that something is not a certain adjective (like "not hard", "not cold", or "not big"), you must always use değil.