Learn Turkish: Bezini değiştirene kadar çok ağlıyor. - He cries a lot until I change his diaper.

This uses the structure you are learning now: verb root (değiştir-) + -ene kadar (until doing). Notice that -ene kadar does not change based on who is doing the action. It literally means "until the changing happens." We know it means "until I change" purely from the context of the situation.

Let's break down the word bezini. Why are there two -i endings?

The root is bez (diaper). The first -i makes it "his diaper" (bezi). The -n- is a buffer letter we always use after a "his/her/its" ending when adding another suffix. The final -i is the accusative case marker, which is needed because "his diaper" is the specific direct object being changed.

The root verb is ağlamak (to cry). Why does it become ağlıyor instead of ağlayor?

When a verb ends in -a or -e (like ağla-), adding the present continuous suffix -ıyor causes that final vowel to drop or "narrow" into ı, i, u, or ü. Here, the -a turns into an -ı, giving us ağlıyor.

Why use değiştirmek instead of değişmek for "to change"?