Valitsimme yhden kehityskohteen syksylle.

Valitsimme means we chose.

It breaks down like this:

• valita = to choose
• valitsi- = past-tense stem
• -mme = we

So:

• valitsimme = we chose

This is the past tense. Finnish often packs the subject into the verb ending, so the word already includes we.

Because Finnish usually does not need a subject pronoun when the verb ending already shows who is doing the action.

Here, -mme tells you the subject is we.

So:

• Valitsimme = we chose
• Me valitsimme = we chose too, but me is added for emphasis or contrast

In a neutral sentence, leaving out me is completely normal.

Because yksi changes form depending on its grammatical role.

Basic form:

• yksi = one

Here it is part of the object of the sentence, and the object is a complete, finished whole: we chose one specific thing. In this kind of sentence, Finnish uses the total object form, which here looks like -n:

• yksi → yhden

So:

• yhden kehityskohteen = one development target / one area for development

This is very common after a completed action in an affirmative sentence.

For the same reason: it is part of the total object.

The object here is:

• yhden kehityskohteen

Both words show the object form:

• yhden
• kehityskohteen

With yksi, the noun behaves a bit like it does after an adjective: both words match the case.

Compare:

• yksi kehityskohde = one development target
• yhden kehityskohteen = one development target (as a complete object)

So the sentence presents the choosing as a completed action affecting one whole, specific item.

It is a compound word:

• kehitys = development
• kohde = target, object, focus, item

So kehityskohde literally means something like:

• development target
• area for development
• area for improvement

In many real contexts, especially business, school, project, or evaluation language, it often means:

• an aspect that should be improved
• a focus area for development

So the English meaning depends a little on context, even if the Finnish grammar stays the same.

Syksylle is the allative form of syksy (autumn / fall).

The ending -lle often means:

• onto
• to
• for

With time words, it often means something like:

• for a certain time
• scheduled/assigned for a certain period

So here:

• syksylle = for the autumn
• more naturally: for autumn

The idea is not just in autumn, but rather chosen for use/focus/scheduling in autumn.

Because syksyllä and syksylle mean different things.

• syksyllä = in the autumn / during autumn
• syksylle = for autumn / for the autumn period

So compare:

• Valitsimme yhden kehityskohteen syksyllä.
  = We chose one development target in autumn.
  This tells you when the choosing happened.

• Valitsimme yhden kehityskohteen syksylle.
  = We chose one development target for autumn.
  This tells you what period it was chosen for.

That difference is very important here.

Normally, yhden still means one.

Finnish has no articles like a, an, or the, so learners often wonder if yksi/yhden is filling that role. Sometimes yksi can feel a little article-like in certain contexts, but its core meaning is still one.

In this sentence, the most natural reading is that the number matters:

• we chose one development target for autumn

So this is not just an indefinite article substitute. It most likely really means one.

No, Finnish word order is fairly flexible, though some orders sound more neutral than others.

This sentence is neutral and natural:

• Valitsimme yhden kehityskohteen syksylle.

But Finnish can move things around for emphasis or topic/focus reasons:

• Syksylle valitsimme yhden kehityskohteen.
  = emphasizes for autumn

• Yhden kehityskohteen valitsimme syksylle.
  = emphasizes one development target

Because the verb ending already shows the subject, starting with the verb here feels perfectly normal.

Yes. The sentence strongly suggests a completed choice.

Two things point to that:

• valitsimme is past tense: we chose
• yhden kehityskohteen is in the total object form, which fits a finished, bounded action

So the sense is:

• the choosing happened
• it was completed
• one specific item was selected

If the sentence were negative, or if the action were incomplete/open-ended, Finnish would often use a different object form, especially the partitive.