Learn Turkish: Kararı geciktirmekle çok zaman kaybediyoruz. - By delaying the decision, we are losing a lot of time.

The suffix -le is the shortened form of ile (with/by). When you attach it directly to the infinitive form of a verb, like geciktirmek (to delay), it creates the meaning "by doing [action]". Therefore, geciktirmekle translates exactly to "by delaying".

Why does karar have the accusative suffix -ı here?

Karar (decision) gets the specific direct object (accusative) suffix -ı because it is the object of the action "delaying". Even though geciktirmek has an infinitive ending and is acting a bit like a noun, it still behaves like a verb internally and takes its own direct object.

I know the verb gecikmek means "to be late". What is the -tir- doing in geciktirmek?

The -tir is a causative suffix. It changes an action into "making someone/something do" that action. So, it changes the intransitive verb gecikmek (to be late) into the transitive verb geciktirmek (to make something late, which means "to delay").

Why are there so many sound changes in kaybediyoruz?