Learn Finnish: Juoksija joi vettä, mutta uupumus oli kuitenkin kova. - The runner drank water, but the exhaustion was severe anyway.

In Finnish, adverbial connectors like kuitenkin usually do not sit at the very start of a clause. They naturally fall after the verb. While you can sometimes see mutta kuitenkin placed together, separating them by putting kuitenkin later sounds highly natural and translates well to adding "anyway" or "still" to the thought.

Since the runner's action of drinking is completed in the past, why is water in the partitive case (vettä)?

Even though the action of drinking is complete in the past tense (joi), water is an uncountable mass noun. Because the runner drank an unspecified amount of water, rather than a specific whole portion like a single bottle, the object must remain in the partitive case.

Where does the noun uupumus come from?

It is built from the verb uupua, which means "to get tired" or "to become exhausted." The suffix -mus is a common way to turn a verb into a noun, representing the state or result of that action, much like the "-tion" ending in English.

I know kova usually means "hard". How does it mean "severe" here?

In Finnish, kova is a versatile word used to express high intensity, not just physical hardness. Just as a wind can be kova tuuli (strong wind) and a noise can be kova ääni (loud noise), a feeling or condition like exhaustion can also be kova (severe or heavy).