Learn Turkish: Kanatları geniş kartal aniden gökyüzünde kayboldu. - The broad-winged eagle suddenly disappeared in the sky.

This is a possessive compound adjective. Instead of the standard adjective order, we use Noun + Possessive + Adjective: kanat-lar-ı (its wings) + geniş (broad). Literally, it acts as a modifier meaning "its wings broad," which translates to "broad-winged."

Could I just say geniş kanatlı kartal instead?

Yes, geniş kanatlı (broad-winged, using the -lI suffix) is perfectly correct and means the same thing. The kanatları geniş structure used here sounds slightly more descriptive or literary, placing a bit more emphasis on the physical feature (the wings) before describing it.

Why does gökyüzünde have an n before the locative suffix -de?

Gökyüzü (sky) is a compound noun formed from gök (sky) and yüz (face) + the 3rd person possessive suffix -ü. As a quick refresher: whenever you attach a case ending (like -de) to a word ending in a 3rd person possessive suffix, Turkish requires the buffer consonant -n-, resulting in gökyüzünde.

Where does the verb kayboldu come from?