Luotettava, tunnollinen ja yhteistyökykyinen kollega tekee aloitteita, kun työssä on ongelma.

Because they all describe kollega, and they agree with it in case and number.

Here, kollega is:

• singular
• nominative (the basic dictionary form)

So the adjectives are also singular nominative:

• luotettava kollega = a reliable colleague
• tunnollinen kollega = a conscientious colleague
• yhteistyökykyinen kollega = a cooperative / able-to-work-with-others colleague

Finnish adjectives usually match the noun they describe.

Finnish does not have articles like English a/an or the.

So kollega can mean:

• a colleague
• the colleague
• sometimes just colleague, depending on context

You figure out which one is meant from the situation, not from a separate article word.

Tehdä aloite / tehdä aloitteita means to make an initiative / to take initiative / to make suggestions or proposals proactively.

Here aloitteita is the partitive plural of aloite.

Why partitive plural? Because it suggests:

• an unspecified number of initiatives
• repeated or general action
• not one single clearly bounded initiative

So:

• tekee aloitteen = makes one specific initiative/proposal
• tekee aloitteita = makes initiatives, takes initiative, comes up with suggestions

In this sentence, the partitive plural sounds natural because it describes a general quality or habit of a good colleague.

Työssä is the inessive case, which usually means in something.

• työ = work
• työssä = in the work / at work

In this sentence, työssä on ongelma means something like:

• there is a problem at work
• there is a problem in the work

The exact English translation depends on context, but the Finnish form -ssa / -ssä marks being inside or within something.

Because this is an existential-type structure in Finnish: it states that something exists somewhere.

The pattern is often:

• [place/situation] + on + [thing]

So:

• työssä on ongelma = there is a problem at work

Here:

• työssä = the setting/location
• on = is
• ongelma = problem

Also, ongelma is in the nominative singular because it refers to one countable problem.

If you said ongelmaa, that would be partitive and would suggest something less bounded, more vague, or would appear in different contexts. In this sentence, ongelma is the normal choice.

Because the subject is still just one person: kollega.

The adjectives do not make the subject plural. They all describe the same singular noun.

So:

• kollega tekee = the colleague does/makes

If the subject were plural, then the verb would be plural too:

• Luotettavat, tunnolliset ja yhteistyökykyiset kollegat tekevät aloitteita.
• Reliable, conscientious, and cooperative colleagues take initiative.

Here kun means when, and in this kind of sentence it can also feel like whenever.

So the idea is:

• a good colleague takes initiative when there is a problem at work

It presents this as a normal or expected situation.

Compare:

• kun = when
• jos = if

If you used jos, the sentence would sound more conditional:

• ... tekee aloitteita, jos työssä on ongelma.
• ... takes initiative if there is a problem at work.

That is possible, but kun fits well when talking about a typical real-life situation.

Because kun työssä on ongelma is a subordinate clause.

Finnish normally uses a comma before subordinate clauses introduced by words like:

• kun = when
• jos = if
• että = that
• koska = because

So the comma here is standard Finnish punctuation.

Yes — it is a long compound-like adjective, and Finnish often builds words this way.

It can be broken down roughly like this:

• yhteistyö = cooperation, working together
• kyky = ability
• -inen = an adjective-forming ending

So yhteistyökykyinen literally means something like:

• having the ability for cooperation
• capable of working together with others

Natural English translations include:

• cooperative
• good at teamwork
• able to collaborate

Yes, historically it is related to tunto, which has meanings connected to feeling, sense, or conscience depending on context.

In modern usage, tunnollinen means someone who:

• does things carefully
• takes responsibility seriously
• is diligent and conscientious

So in workplace language, tunnollinen is often a very positive adjective for a reliable worker.

It is a normal and useful expression, especially in:

• workplace language
• job ads
• performance reviews
• discussions of professional qualities

It often describes someone who is proactive.

Depending on context, related expressions are:

• olla aloitteellinen = to be proactive / show initiative
• tehdä aloite = make a proposal / initiative
• tehdä aloitteita = make proposals / take initiative repeatedly or generally

So this sentence sounds quite natural in a professional context.

Yes. A very natural alternative would be:

Luotettava, tunnollinen ja yhteistyökykyinen kollega on aloitteellinen, kun työssä on ongelma.

That means roughly:

• A reliable, conscientious, and cooperative colleague is proactive when there is a problem at work.

The difference is:

• tekee aloitteita focuses on the action
• on aloitteellinen focuses on the quality/trait

Both are good Finnish, but the original sentence emphasizes what the colleague actually does.

Yes, very normal.

In existential sentences, Finnish often puts:

1. the place or setting first
2. then on
3. then the thing that exists

So:

• työssä on ongelma = at work / in the work there is a problem

This is one of the most common Finnish patterns.

A learner may expect something more like English word order, but Finnish often prefers this structure when introducing the existence of something.