Learn Croatian: Položit ću ispit umjesto da paničarim. - I will pass the exam instead of panicking.

In English, we use "instead of" followed by an "-ing" verb (a gerund). Croatian doesn't work this way. You must use the conjunction phrase umjesto da (literally "instead that") followed by a standard conjugated verb. So, umjesto da paničarim translates literally to "instead that I panic".

Why is the final "i" missing in Položit ću? Shouldn't the infinitive be položiti?

Yes, the infinitive is položiti. However, there is a spelling and pronunciation rule for the future tense: if a verb ending in -ti comes immediately before the future clitic (ću, ćeš, etc.), the final -i is dropped. If you used a pronoun first, the -i would stay: Ja ću položiti.

I often mix up taking an exam and passing an exam. Does položiti ispit guarantee that I passed?

Yes! Položiti is a perfective verb that specifically means you successfully passed the exam. If you want to say you are just taking an exam and don't know the result yet, you would use the imperfective form polagati ispit or the phrase pisati ispit (literally "to write an exam").

This lesson is about feelings like strah me je (I am afraid). How would I adapt this sentence to say "instead of being afraid"?