Learn Finnish: Hän valitsee akupunktion sen sijaan että ottaisi pillerin. - He chooses acupuncture instead of taking a pill.

The phrase sen sijaan että (instead of) introduces an alternative action that isn't actually happening. Because this action is hypothetical, Finnish naturally uses the conditional mood (ottaisi, would take) rather than the basic present tense.

In English we say 'instead of taking', using an -ing word. Why does Finnish use että plus a fully conjugated verb?

While English uses 'instead of' followed by an -ing verb, the Finnish conjunction sen sijaan että literally translates to 'instead of that [he would take]'. It requires a full clause with a conjugated verb rather than a single verb form.

Why do the words akupunktion and pillerin both end in -n?

They are both total objects. Hän valitsee (he chooses) takes the object akupunktion, and ottaisi (he would take) takes the object pillerin. Since both verbs express complete actions, their objects take the genitive-accusative -n ending.

Why isn't there a word for 'he' before ottaisi?

The subject of the first clause is hän. When the subject of the että clause is exactly the same person, you don't need to repeat the pronoun in Finnish. The verb ottaisi belongs to the same subject.