Learn Turkish: Patron çok düşündükten sonra sarı dosyada karar kıldı. - After thinking a lot, the boss settled on the yellow file.

This is because of the verb karar kılmak (to settle on). Unlike karar vermek (to decide), which takes the dative case (like giving a decision 'to' something), karar kılmak requires the locative case. You can think of it as your final choice resting 'in' or 'at' a specific option after considering several alternatives.

What is the exact difference between karar kılmak and the more common karar vermek?

Karar vermek is the general verb for 'to decide' (e.g., deciding to leave, deciding on a plan). Karar kılmak specifically means 'to settle on' or 'to make a final selection' from a group of choices. In this sentence, the boss likely looked at multiple colored files before finally settling on the yellow one.

What is the word kıldı in this sentence?

It is the past tense of kılmak, which is an auxiliary verb similar to etmek and yapmak. While it is rarely used to create new verbs in everyday modern Turkish, it survives in several fixed compound verbs you will encounter at the B2 level, such as karar kılmak (to settle on), namaz kılmak (to perform Islamic prayer), and mümkün kılmak (to make possible).

Let's review düşündükten sonra. How is this 'after doing' structure built here?