Täytän vesipullon ennen lähtöä, sehän on tärkeää.

Sehän is se (it) + the clitic -hän/-hän. The clitic adds a nuance like “as you know,” “after all,” or “you see,” presenting the statement as shared/obvious information or a gentle reminder. It’s often used to:

• Soften assertions and commands.
• Seek agreement or build rapport.
• Emphasize something the speaker thinks should be evident.

Compare:

• Se on tärkeää. It is important. (neutral)
• Sehän on tärkeää. It’s important, after all / as you know it is.

Note: This -hän is a clitic particle, not the pronoun hän (“he/she”).

With abstract or clause-like subjects (here, se refers to the whole idea “filling the bottle before leaving”), Finnish typically uses a partitive predicative: Se on tärkeää (“That is important” in a general, non-countable sense). Use nominative (tärkeä) when describing a concrete, countable noun:

• Se koira on tärkeä. That dog is important.
• But: Se on tärkeää = “That (fact/action) is important.”

It’s the object in a “complete” action, so it appears in the (genitive-form) accusative: vesipullo → vesipullon. Finnish marks “total” objects with this -n form in the singular.

• Täytän vesipullon. I (will) fill the bottle (to completion).
• If the action is ongoing/partial, the object is partitive: Täytän vesipulloa (“I’m filling the bottle,” not necessarily to completion).

The preposition ennen (“before”) governs the partitive. So you use ennen + partitive:

• ennen lähtöä = before (the) departure. By contrast, jälkeen (“after”) governs the genitive:
• lähdön jälkeen = after (the) departure.

Yes. Use ennen kuin + a finite verb:

• Täytän vesipullon ennen kuin lähden. I fill the water bottle before I leave. Rule of thumb:
• ennen + partitive noun (ennen lähtöä)
• ennen kuin + clause (ennen kuin lähden)

Correct—Finnish has no dedicated future tense. Täytän (1st person singular present of täyttää) covers both present and near-future. Context supplies the time:

• Here, with ennen (“before”), it naturally reads as a future plan: “I’ll fill…”

Personal pronouns are usually dropped because the verb ending shows the person. Täytän already means “I fill.” You can add minä for emphasis or contrast:

• Minä täytän vesipullon… (I, as opposed to someone else, will fill…)

Absolutely. Possession can be shown with the possessive suffix:

• vesipulloni = my water bottle You could also say minun vesipulloni (explicit “my”), or just vesipullon if ownership is clear from context.

Yes, Finnish word order is flexible for emphasis/information flow:

• Ennen lähtöä täytän vesipullon, sehän on tärkeää. (Fronts the time.)
• Vesipullon täytän ennen lähtöä… (Emphasizes the object.) The core grammar (cases and endings) keeps the meaning clear.

They’re distinct:

• sehän = se
  • clitic -hän (“it, after all”).
• hän alone is the 3rd-person human pronoun “he/she.” Context and form keep them separate.